From 5512ccdb63370be27a387acab0c1ae366607b089 Mon Sep 17 00:00:00 2001 From: xll <18574553598@163.com> Date: Sat, 29 May 2021 10:44:58 +0800 Subject: [PATCH 01/41] =?UTF-8?q?0513=E4=BA=8C=E5=8F=89=E6=A0=91=E5=B7=A6?= =?UTF-8?q?=E5=B0=8F=E8=A7=92=E7=9A=84=E5=80=BCJavaScript=E7=89=88?= =?UTF-8?q?=E6=9C=AC?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- problems/0513.找树左下角的值.md | 47 ++++++++++++++++++++++++++ 1 file changed, 47 insertions(+) diff --git a/problems/0513.找树左下角的值.md b/problems/0513.找树左下角的值.md index 5c9613e5..97464e3d 100644 --- a/problems/0513.找树左下角的值.md +++ b/problems/0513.找树左下角的值.md @@ -298,6 +298,53 @@ class Solution: ``` Go： +JavaScript: +1. 递归版本 +```javascript +var findBottomLeftValue = function(root) { + //首先考虑递归遍历 前序遍历 找到最大深度的叶子节点即可 + let maxPath = 0,resNode = null; + // 1. 确定递归函数的函数参数 + const dfsTree = function(node,curPath){ + // 2. 确定递归函数终止条件 + if(node.left===null&&node.right===null){ + if(curPath>maxPath){ + maxPath = curPath; + resNode = node.val; + } + // return ; + } + node.left&&dfsTree(node.left,curPath+1); + node.right&&dfsTree(node.right,curPath+1); + } + dfsTree(root,1); + return resNode; +}; +``` +2. 层序遍历 +```javascript +var findBottomLeftValue = function(root) { + //考虑层序遍历 记录最后一行的第一个节点 + let queue = []; + if(root===null){ + return null; + } + queue.push(root); + let resNode; + while(queue.length){ + let length = queue.length; + for(let i=0; i Date: Sat, 29 May 2021 12:50:49 +0800 Subject: [PATCH 02/41] =?UTF-8?q?=E6=B7=BB=E5=8A=A0=E4=BA=861047-golang?= =?UTF-8?q?=E7=89=88=E6=9C=AC?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- ...除字符串中的所有相邻重复项.md | 17 +++++++++++++++++ 1 file changed, 17 insertions(+) diff --git a/problems/1047.删除字符串中的所有相邻重复项.md b/problems/1047.删除字符串中的所有相邻重复项.md index 9ca08c96..305a287d 100644 --- a/problems/1047.删除字符串中的所有相邻重复项.md +++ b/problems/1047.删除字符串中的所有相邻重复项.md @@ -186,6 +186,23 @@ class Solution: Go： +```go +func removeDuplicates(s string) string { + var stack []byte + for i := 0; i < len(s);i++ { + // 栈不空 且 与栈顶元素不等 + if len(stack) > 0 && stack[len(stack)-1] == s[i] { + // 弹出栈顶元素 并 忽略当前元素(s[i]) + stack = stack[:len(stack)-1] + }else{ + // 入栈 + stack = append(stack, s[i]) + } + } + return string(stack) +} +``` + javaScript: ```js From fb91b760eb6fa0583210ca260b77f71418787ab8 Mon Sep 17 00:00:00 2001 From: hk27xing <244798299@qq.com> Date: Sat, 29 May 2021 16:13:32 +0800 Subject: [PATCH 03/41] =?UTF-8?q?=E7=BA=A0=E6=AD=A339.=E7=BB=84=E5=90=88?= =?UTF-8?q?=E6=80=BB=E5=92=8C=20Java=E7=89=88=E6=9C=AC=E4=BB=A3=E7=A0=81?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- problems/0039.组合总和.md | 40 +++++++++++++++-------------------- 1 file changed, 17 insertions(+), 23 deletions(-) diff --git a/problems/0039.组合总和.md b/problems/0039.组合总和.md index ab118ee0..a83e42f4 100644 --- a/problems/0039.组合总和.md +++ b/problems/0039.组合总和.md @@ -237,34 +237,28 @@ public: Java： ```Java +// 剪枝优化 class Solution { - List> lists = new ArrayList<>(); - Deque deque = new LinkedList<>(); - - public List> combinationSum3(int k, int n) { - int[] arr = new int[]{1, 2, 3, 4, 5, 6, 7, 8, 9}; - backTracking(arr, n, k, 0); - return lists; + public List> combinationSum(int[] candidates, int target) { + List> res = new ArrayList<>(); + Arrays.sort(candidates); // 先进行排序 + backtracking(res, new ArrayList<>(), candidates, target, 0, 0); + return res; } - public void backTracking(int[] arr, int n, int k, int startIndex) { - //如果 n 小于0，没必要继续本次递归，已经不符合要求了 - if (n < 0) { + public void backtracking(List> res, List path, int[] candidates, int target, int sum, int idx) { + // 找到了数字和为 target 的组合 + if (sum == target) { + res.add(new ArrayList<>(path)); return; } - if (deque.size() == k) { - if (n == 0) { - lists.add(new ArrayList(deque)); - } - return; - } - for (int i = startIndex; i < arr.length - (k - deque.size()) + 1; i++) { - deque.push(arr[i]); - //减去当前元素 - n -= arr[i]; - backTracking(arr, n, k, i + 1); - //恢复n - n += deque.pop(); + + for (int i = idx; i < candidates.length; i++) { + // 如果 sum + candidates[i] > target 就终止遍历 + if (sum + candidates[i] > target) break; + path.add(candidates[i]); + backtracking(res, path, candidates, target, sum + candidates[i], i); + path.remove(path.size() - 1); // 回溯，移除路径 path 最后一个元素 } } } From b1b389da3204c4faf0c65519e8f58cf59afe18d4 Mon Sep 17 00:00:00 2001 From: xll <18574553598@163.com> Date: Sat, 29 May 2021 22:20:52 +0800 Subject: [PATCH 04/41] =?UTF-8?q?=E4=BA=8C=E5=8F=89=E6=A0=91=E8=B7=AF?= =?UTF-8?q?=E5=BE=84=E6=80=BB=E5=92=8CJavaScript=E7=89=88=E6=9C=AC?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- problems/0112.路径总和.md | 56 +++++++++++++++++++++++++++++++++++ 1 file changed, 56 insertions(+) diff --git a/problems/0112.路径总和.md b/problems/0112.路径总和.md index b4a3f38b..4ccd8912 100644 --- a/problems/0112.路径总和.md +++ b/problems/0112.路径总和.md @@ -524,6 +524,62 @@ let pathSum = function (root, targetSum) { }; ``` +0112 路径总和 +```javascript +var hasPathSum = function(root, targetSum) { + //递归方法 + // 1. 确定函数参数 + const traversal = function(node,count){ + // 2. 确定终止条件 + if(node.left===null&&node.right===null&&count===0){ + return true; + } + if(node.left===null&&node.right===null){ + return false; + } + //3. 单层递归逻辑 + if(node.left){ + if(traversal(node.left,count-node.left.val)){ + return true; + } + } + if(node.right){ + if(traversal(node.right,count-node.right.val)){ + return true; + } + } + return false; + } + if(root===null){ + return false; + } + return traversal(root,targetSum-root.val); +}; +``` +113 路径总和 +```javascript +var pathSum = function(root, targetSum) { + //递归方法 + let resPath = [],curPath = []; + // 1. 确定递归函数参数 + const travelTree = function(node,count){ + curPath.push(node.val); + count-=node.val; + if(node.left===null&&node.right===null&&count===0){ + resPath.push([...curPath]); + } + node.left&&travelTree(node.left,count); + node.right&&travelTree(node.right,count); + let cur = curPath.pop(); + count-=cur; + } + if(root===null){ + return resPath; + } + travelTree(root,targetSum); + return resPath; +}; +``` From 406d44819ac878232b49a6ffafad06d944643a6a Mon Sep 17 00:00:00 2001 From: X-shuffle <53906918+X-shuffle@users.noreply.github.com> Date: Sun, 30 May 2021 10:38:30 +0800 Subject: [PATCH 05/41] =?UTF-8?q?=E6=B7=BB=E5=8A=A0=20=E4=BA=8C=E5=8F=89?= =?UTF-8?q?=E6=A0=91=E7=9A=84=E5=B1=82=E5=BA=8F=E9=81=8D=E5=8E=86=20GO?= =?UTF-8?q?=E7=89=88=E6=9C=AC?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 添加 二叉树的层序遍历 GO版本 --- problems/0102.二叉树的层序遍历.md | 243 ++++++++++++++++++++++ 1 file changed, 243 insertions(+) diff --git a/problems/0102.二叉树的层序遍历.md b/problems/0102.二叉树的层序遍历.md index ee93911e..00607082 100644 --- a/problems/0102.二叉树的层序遍历.md +++ b/problems/0102.二叉树的层序遍历.md @@ -836,6 +836,249 @@ func levelOrder(root *TreeNode) [][]int { return result } ``` +> 二叉树的层序遍历（GO语言完全版） + +```go +/** +102. 二叉树的层序遍历 + */ +func levelOrder(root *TreeNode) [][]int { + res:=[][]int{} + if root==nil{//防止为空 + return res + } + queue:=list.New() + queue.PushBack(root) + var tmpArr []int + for queue.Len()>0 { + length:=queue.Len()//保存当前层的长度，然后处理当前层（十分重要，防止添加下层元素影响判断层中元素的个数） + for i:=0;i0{ + length:=queue.Len() + tmp:=[]int{} + for i:=0;i0{ + length:=queue.Len() + tmp:=[]int{} + for i:=0;i0 { + length:=queue.Len()//保存当前层的长度，然后处理当前层（十分重要，防止添加下层元素影响判断层中元素的个数） + for i:=0;i0{ + length:=queue.Len()//记录当前层的数量 + var tmp []int + for T:=0;T0 { + length:=queue.Len()//保存当前层的长度，然后处理当前层（十分重要，防止添加下层元素影响判断层中元素的个数） + for i:=0;i max { + max = val + } + } + return max +} +/** +116. 填充每个节点的下一个右侧节点指针 +117. 填充每个节点的下一个右侧节点指针 II + */ + +func connect(root *Node) *Node { + res:=[][]*Node{} + if root==nil{//防止为空 + return root + } + queue:=list.New() + queue.PushBack(root) + var tmpArr []*Node + for queue.Len()>0 { + length:=queue.Len()//保存当前层的长度，然后处理当前层（十分重要，防止添加下层元素影响判断层中元素的个数） + for i:=0;i Date: Sun, 30 May 2021 19:21:51 +0800 Subject: [PATCH 06/41] =?UTF-8?q?Update=200416.=E5=88=86=E5=89=B2=E7=AD=89?= =?UTF-8?q?=E5=92=8C=E5=AD=90=E9=9B=86.md?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Added python version code --- problems/0416.分割等和子集.md | 14 ++++++++++++-- 1 file changed, 12 insertions(+), 2 deletions(-) diff --git a/problems/0416.分割等和子集.md b/problems/0416.分割等和子集.md index e69eb1a4..55d200e2 100644 --- a/problems/0416.分割等和子集.md +++ b/problems/0416.分割等和子集.md @@ -222,8 +222,18 @@ class Solution { ``` Python： - - +```python +class Solution: + def canPartition(self, nums: List[int]) -> bool: + taraget = sum(nums) + if taraget % 2 == 1: return False + taraget //= 2 + dp = [0] * 10001 + for i in range(len(nums)): + for j in range(taraget, nums[i] - 1, -1): + dp[j] = max(dp[j], dp[j - nums[i]] + nums[i]) + return taraget == dp[taraget] +``` Go： From 1516dc3d152b818f1e3d4f3675924c35918e0558 Mon Sep 17 00:00:00 2001 From: resyon Date: Sun, 30 May 2021 21:27:11 +0800 Subject: [PATCH 07/41] =?UTF-8?q?=E6=B7=BB=E5=8A=A0=E4=BA=860239-golang?= =?UTF-8?q?=E7=89=88=E6=9C=AC?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- problems/0239.滑动窗口最大值.md | 30 ++++++++++++++++++++++++++ 1 file changed, 30 insertions(+) diff --git a/problems/0239.滑动窗口最大值.md b/problems/0239.滑动窗口最大值.md index 6cc355ca..ed17157a 100644 --- a/problems/0239.滑动窗口最大值.md +++ b/problems/0239.滑动窗口最大值.md @@ -267,6 +267,36 @@ Python： Go： +```go +func maxSlidingWindow(nums []int, k int) []int { + var queue []int + var rtn []int + + for f := 0; f < len(nums); f++ { + //维持队列递减, 将 k 插入合适的位置, queue中 <=k 的 元素都不可能是窗口中的最大值, 直接弹出 + for len(queue) > 0 && nums[f] > nums[queue[len(queue)-1]] { + queue = queue[:len(queue)-1] + } + // 等大的后来者也应入队 + if len(queue) == 0 || nums[f] <= nums[queue[len(queue)-1]] { + queue = append(queue, f) + } + + if f >= k - 1 { + rtn = append(rtn, nums[queue[0]]) + //弹出离开窗口的队首 + if f - k + 1 == queue[0] { + queue = queue[1:] + } + } + } + + return rtn + +} + +``` + Javascript: ```javascript var maxSlidingWindow = function (nums, k) { From 0de459b1ff5f491e13c4fec93cbc7727dabc73e6 Mon Sep 17 00:00:00 2001 From: LiangDazhu <42199191+LiangDazhu@users.noreply.github.com> Date: Sun, 30 May 2021 22:54:01 +0800 Subject: [PATCH 08/41] =?UTF-8?q?Update=20=E8=83=8C=E5=8C=85=E7=90=86?= =?UTF-8?q?=E8=AE=BA=E5=9F=BA=E7=A1=8001=E8=83=8C=E5=8C=85-2.md?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit dp[j]可以通过dp[j - weight[i]]推导出来, 应该是写错了吧 --- problems/背包理论基础01背包-2.md | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/problems/背包理论基础01背包-2.md b/problems/背包理论基础01背包-2.md index a169425a..e831d88f 100644 --- a/problems/背包理论基础01背包-2.md +++ b/problems/背包理论基础01背包-2.md @@ -55,7 +55,7 @@ dp[j]为 容量为j的背包所背的最大价值，那么如何推导dp[j]呢？ -dp[j]可以通过dp[j - weight[j]]推导出来，dp[j - weight[i]]表示容量为j - weight[i]的背包所背的最大价值。 +dp[j]可以通过dp[j - weight[i]]推导出来，dp[j - weight[i]]表示容量为j - weight[i]的背包所背的最大价值。 dp[j - weight[i]] + value[i] 表示 容量为 j - 物品i重量 的背包 加上 物品i的价值。（也就是容量为j的背包，放入物品i了之后的价值即：dp[j]） From 60ad3b081134174577ad58416d275b1bb78267cd Mon Sep 17 00:00:00 2001 From: fusunx <1102654482@qq.com> Date: Sun, 30 May 2021 23:37:15 +0800 Subject: [PATCH 09/41] =?UTF-8?q?0045.=E8=B7=B3=E8=B7=83=E6=B8=B8=E6=88=8F?= =?UTF-8?q?||.md=20Javascript?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- problems/0045.跳跃游戏II.md | 20 ++++++++++++++++++++ 1 file changed, 20 insertions(+) diff --git a/problems/0045.跳跃游戏II.md b/problems/0045.跳跃游戏II.md index 31b52b31..4128da4c 100644 --- a/problems/0045.跳跃游戏II.md +++ b/problems/0045.跳跃游戏II.md @@ -208,6 +208,26 @@ func jump(nums []int) int { } return dp[len(nums)-1] } +``` + +Javascript: +```Javascript +var jump = function(nums) { + let curIndex = 0 + let nextIndex = 0 + let steps = 0 + for(let i = 0; i < nums.length - 1; i++) { + nextIndex = Math.max(nums[i] + i, nextIndex) + if(i === curIndex) { + curIndex = nextIndex + steps++ + } + } + + return steps +}; +``` + /* dp[i]表示从起点到当前位置的最小跳跃次数 dp[i]=min(dp[j]+1,dp[i]) 表示从j位置用一步跳跃到当前位置，这个j位置可能有很多个，却最小一个就可以 From e9c91e78998bde1a123865df30aca4071bba8159 Mon Sep 17 00:00:00 2001 From: "qingyi.liu" Date: Mon, 31 May 2021 10:55:43 +0800 Subject: [PATCH 10/41] =?UTF-8?q?=E4=BA=8C=E5=8F=89=E6=A0=91=E7=9A=84?= =?UTF-8?q?=E7=BB=9F=E4=B8=80=E8=BF=AD=E4=BB=A3=E6=B3=95=20javaScript?= =?UTF-8?q?=E7=89=88=E6=9C=AC?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- problems/二叉树的统一迭代法.md | 80 +++++++++++++++++++++++++ 1 file changed, 80 insertions(+) diff --git a/problems/二叉树的统一迭代法.md b/problems/二叉树的统一迭代法.md index dca5d3e3..f4091ad5 100644 --- a/problems/二叉树的统一迭代法.md +++ b/problems/二叉树的统一迭代法.md @@ -374,6 +374,86 @@ func postorderTraversal(root *TreeNode) []int { } ``` +javaScript: + +> 前序遍历统一迭代法 + +```js + +// 前序遍历：中左右 +// 压栈顺序：右左中 + +var preorderTraversal = function(root, res = []) { + const stack = []; + if (root) stack.push(root); + while(stack.length) { + const node = stack.pop(); + if(!node) { + res.push(stack.pop().val); + continue; + } + if (node.right) stack.push(node.right); // 右 + if (node.left) stack.push(node.left); // 左 + stack.push(node); // 中 + stack.push(null); + }; + return res; +}; + +``` + +> 中序遍历统一迭代法 + +```js + +// 中序遍历：左中右 +// 压栈顺序：右中左 + +var inorderTraversal = function(root, res = []) { + const stack = []; + if (root) stack.push(root); + while(stack.length) { + const node = stack.pop(); + if(!node) { + res.push(stack.pop().val); + continue; + } + if (node.right) stack.push(node.right); // 右 + stack.push(node); // 中 + stack.push(null); + if (node.left) stack.push(node.left); // 左 + }; + return res; +}; + +``` + +> 后序遍历统一迭代法 + +```js + +// 后续遍历：左右中 +// 压栈顺序：中右左 + +var postorderTraversal = function(root, res = []) { + const stack = []; + if (root) stack.push(root); + while(stack.length) { + const node = stack.pop(); + if(!node) { + res.push(stack.pop().val); + continue; + } + stack.push(node); // 中 + stack.push(null); + if (node.right) stack.push(node.right); // 右 + if (node.left) stack.push(node.left); // 左 + }; + return res; +}; + +``` + ----------------------- From 18a37ec17d2e596d12f37373b0decffded380f76 Mon Sep 17 00:00:00 2001 From: "qingyi.liu" Date: Mon, 31 May 2021 15:25:34 +0800 Subject: [PATCH 11/41] =?UTF-8?q?=E4=BA=8C=E5=8F=89=E6=A0=91=E7=9A=84?= =?UTF-8?q?=E5=B1=82=E5=BA=8F=E9=81=8D=E5=8E=86=20=E4=B8=80=E5=A5=97?= =?UTF-8?q?=E6=89=93=E5=85=AB=E4=B8=AAJavaScript=20=E8=BF=AD=E4=BB=A3=20+?= =?UTF-8?q?=20=E9=80=92=E5=BD=92=E7=89=88=E6=9C=AC?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- problems/0102.二叉树的层序遍历.md | 270 ++++++++++++++++++++++ 1 file changed, 270 insertions(+) diff --git a/problems/0102.二叉树的层序遍历.md b/problems/0102.二叉树的层序遍历.md index 00607082..2be38bc4 100644 --- a/problems/0102.二叉树的层序遍历.md +++ b/problems/0102.二叉树的层序遍历.md @@ -1100,6 +1100,276 @@ var levelOrder = function (root) { }; ``` +> 二叉树的层序遍历（Javascript语言完全版） (迭代 + 递归) + +```js +/** + * 102. 二叉树的层序遍历 + * @param {TreeNode} root + * @return {number[][]} + */ + +// 迭代 + +var levelOrder = function(root) { + const queue = [], res = []; + root && queue.push(root); + while(len = queue.length) { + const val = []; + while(len--) { + const node = queue.shift(); + val.push(node.val); + node.left && queue.push(node.left); + node.right && queue.push(node.right); + } + res.push(val); + } + return res; +}; + +// 递归 +var levelOrder = function(root) { + const res = []; + function defs (root, i) { + if(!root) return; + if(!res[i]) res[i] = []; + res[i].push(root.val) + root.left && defs(root.left, i + 1); + root.right && defs(root.right, i + 1); + } + defs(root, 0); + return res; +}; + + +/** + * 107. 二叉树的层序遍历 II + * @param {TreeNode} root + * @return {number[][]} + */ + +// 迭代 + +var levelOrderBottom = function(root) { + const queue = [], res = []; + root && queue.push(root); + while(len = queue.length) { + const val = []; + while(len--) { + const node = queue.shift(); + val.push(node.val); + node.left && queue.push(node.left); + node.right && queue.push(node.right); + } + res.push(val); + } + return res.reverse() +}; + +// 递归 + +var levelOrderBottom = function(root) { + const res = []; + function defs (root, i) { + if(!root) return; + if(!res[i]) res[i] = []; + res[i].push(root.val); + root.left && defs(root.left, i + 1); + root.right && defs(root.right, i + 1); + } + defs(root, 0); + return res.reverse(); +}; + +/** + * 199. 二叉树的右视图 + * @param {TreeNode} root + * @return {number[]} + */ + +// 迭代 + +var rightSideView = function(root) { + const res = [], queue = []; + root && queue.push(root); + while(l = queue.length) { + while (l--) { + const {val, left, right} = queue.shift(); + !l && res.push(val); + left && queue.push(left); + right && queue.push(right); + } + } + return res; +}; + +// 递归 +var rightSideView = function(root) { + const res = []; + function defs(root, i) { + if(!root) return; + res[i] = root.val; + root.left && defs(root.left, i + 1); + root.right && defs(root.right, i + 1); + } + defs(root, 0); + return res; +}; + +/** + * 637. 二叉树的层平均值 + * @param {TreeNode} root + * @return {number[]} + */ + +// 迭代 +var averageOfLevels = function(root) { + const stack = [], res = []; + root && stack.push(root); + while(len = stack.length) { + let sum = 0, l = len; + while(l--) { + const {val, left, right} = stack.shift(); + sum += val; + left && stack.push(left); + right && stack.push(right); + } + res.push(sum/len); + } + return res; +}; + +// 递归 +var averageOfLevels = function(root) { + const resCount = [], res = []; + function defs(root, i) { + if(!root) return; + if(isNaN(res[i])) resCount[i] = res[i] = 0; + res[i] += root.val; + resCount[i]++; + root.left && defs(root.left, i + 1); + root.right && defs(root.right, i + 1); + } + defs(root, 0); + return res.map((val, i) => val / resCount[i]); +}; + +/** + * 515. 在每个树行中找最大值 + * @param {TreeNode} root + * @return {number[]} + */ + +// 迭代 +const MIN_G = Number.MIN_SAFE_INTEGER; +var largestValues = function(root) { + const stack = [], res = []; + root && stack.push(root); + while(len = stack.length) { + let max = MIN_G; + while(len--) { + const {val, left, right} = stack.shift(); + max = max > val ? max : val; + left && stack.push(left); + right && stack.push(right); + } + res.push(max); + } + return res; +}; + +// 递归 +var largestValues = function(root) { + const res = []; + function defs (root, i) { + if(!root) return; + if(isNaN(res[i])) res[i] = root.val; + res[i] = res[i] > root.val ? res[i] : root.val; + root.left && defs(root.left, i + 1); + root.right && defs(root.right, i + 1); + } + defs(root, 0); + return res; +}; + +/** + * 429. N 叉树的层序遍历 + * @param {Node|null} root + * @return {number[][]} + */ + +// 迭代 +var levelOrder = function(root) { + const stack = [], res = []; + root && stack.push(root); + while(len = stack.length) { + const vals = []; + while(len--) { + const {val, children} = stack.shift(); + vals.push(val); + for(const e of children) { + stack.push(e); + } + } + res.push(vals); + } + return res; +}; + +// 递归 + +var levelOrder = function(root) { + const res = []; + function defs (root, i) { + if(!root) return; + if(!res[i]) res[i] = []; + res[i].push(root.val); + for(const e of root.children) { + defs(e, i + 1); + } + } + defs(root, 0); + return res; +}; + +/** + * 116. 填充每个节点的下一个右侧节点指针 + * 117. 填充每个节点的下一个右侧节点指针 II + * @param {Node} root + * @return {Node} + */ + +// 迭代 +var connect = function(root) { + const stack = []; + root && stack.push(root); + while(len = stack.length) { + while(len--) { + const node1 = stack.shift(), + node2 = len ? stack[0] : null; + node1.next = node2; + node1.left && stack.push(node1.left); + node1.right && stack.push(node1.right); + } + } + return root; +}; + +// 递归 +var connect = function(root) { + const res = []; + function defs (root, i) { + if(!root) return; + if(res[i]) res[i].next = root; + res[i] = root; + root.left && defs(root.left, i + 1); + root.right && defs(root.right, i + 1); + } + defs(root, 0); + return root; +}; +``` + ----------------------- * 作者微信：[程序员Carl](https://mp.weixin.qq.com/s/b66DFkOp8OOxdZC_xLZxfw) * B站视频：[代码随想录](https://space.bilibili.com/525438321) From 4a5c0cb75b1c265f2dacfb3826dccdb3f0bdae98 Mon Sep 17 00:00:00 2001 From: "qingyi.liu" Date: Mon, 31 May 2021 17:19:02 +0800 Subject: [PATCH 12/41] update: stack to queue --- problems/0102.二叉树的层序遍历.md | 48 +++++++++++------------ 1 file changed, 24 insertions(+), 24 deletions(-) diff --git a/problems/0102.二叉树的层序遍历.md b/problems/0102.二叉树的层序遍历.md index 2be38bc4..51bd8510 100644 --- a/problems/0102.二叉树的层序遍历.md +++ b/problems/0102.二叉树的层序遍历.md @@ -1224,15 +1224,15 @@ var rightSideView = function(root) { // 迭代 var averageOfLevels = function(root) { - const stack = [], res = []; - root && stack.push(root); - while(len = stack.length) { + const queue = [], res = []; + root && queue.push(root); + while(len = queue.length) { let sum = 0, l = len; while(l--) { - const {val, left, right} = stack.shift(); + const {val, left, right} = queue.shift(); sum += val; - left && stack.push(left); - right && stack.push(right); + left && queue.push(left); + right && queue.push(right); } res.push(sum/len); } @@ -1263,15 +1263,15 @@ var averageOfLevels = function(root) { // 迭代 const MIN_G = Number.MIN_SAFE_INTEGER; var largestValues = function(root) { - const stack = [], res = []; - root && stack.push(root); - while(len = stack.length) { + const queue = [], res = []; + root && queue.push(root); + while(len = queue.length) { let max = MIN_G; while(len--) { - const {val, left, right} = stack.shift(); + const {val, left, right} = queue.shift(); max = max > val ? max : val; - left && stack.push(left); - right && stack.push(right); + left && queue.push(left); + right && queue.push(right); } res.push(max); } @@ -1300,15 +1300,15 @@ var largestValues = function(root) { // 迭代 var levelOrder = function(root) { - const stack = [], res = []; - root && stack.push(root); - while(len = stack.length) { + const queue = [], res = []; + root && queue.push(root); + while(len = queue.length) { const vals = []; while(len--) { - const {val, children} = stack.shift(); + const {val, children} = queue.shift(); vals.push(val); for(const e of children) { - stack.push(e); + queue.push(e); } } res.push(vals); @@ -1341,15 +1341,15 @@ var levelOrder = function(root) { // 迭代 var connect = function(root) { - const stack = []; - root && stack.push(root); - while(len = stack.length) { + const queue = []; + root && queue.push(root); + while(len = queue.length) { while(len--) { - const node1 = stack.shift(), - node2 = len ? stack[0] : null; + const node1 = queue.shift(), + node2 = len ? queue[0] : null; node1.next = node2; - node1.left && stack.push(node1.left); - node1.right && stack.push(node1.right); + node1.left && queue.push(node1.left); + node1.right && queue.push(node1.right); } } return root; From 17b8c2d9acb2481783b7820717a0db989c0dd961 Mon Sep 17 00:00:00 2001 From: Lulu Date: Mon, 31 May 2021 20:37:11 +0800 Subject: [PATCH 13/41] fix typo --- .../关于时间复杂度，你不知道的都在这里！.md | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/problems/前序/关于时间复杂度，你不知道的都在这里！.md b/problems/前序/关于时间复杂度，你不知道的都在这里！.md index bd3bd284..3f5bc156 100644 --- a/problems/前序/关于时间复杂度，你不知道的都在这里！.md +++ b/problems/前序/关于时间复杂度，你不知道的都在这里！.md @@ -117,7 +117,7 @@ O(2 * n^2 + 10 * n + 1000) < O(3 * n^2)，所以说最后省略掉常数项系 ![时间复杂度1.png](https://img-blog.csdnimg.cn/20200728191447349.png) -假如有两个算法的时间复杂度，分别是log以2为底n的对数和log以10为底n的对数，那么这里如果还记得高中数学的话，应该不能理解`以2为底n的对数 = 以2为底10的对数 * 以10为底n的对数`。 +假如有两个算法的时间复杂度，分别是log以2为底n的对数和log以10为底n的对数，那么这里如果还记得高中数学的话，应该不难理解`以2为底n的对数 = 以2为底10的对数 * 以10为底n的对数`。 而以2为底10的对数是一个常数，在上文已经讲述了我们计算时间复杂度是忽略常数项系数的。 From 276a7b1e14ca7a54ac9826bde248e0a1c6833444 Mon Sep 17 00:00:00 2001 From: LiangDazhu <42199191+LiangDazhu@users.noreply.github.com> Date: Mon, 31 May 2021 21:34:11 +0800 Subject: [PATCH 14/41] =?UTF-8?q?Update=201049.=E6=9C=80=E5=90=8E=E4=B8=80?= =?UTF-8?q?=E5=9D=97=E7=9F=B3=E5=A4=B4=E7=9A=84=E9=87=8D=E9=87=8FII.md?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Added python version code --- problems/1049.最后一块石头的重量II.md | 12 +++++++++++- 1 file changed, 11 insertions(+), 1 deletion(-) diff --git a/problems/1049.最后一块石头的重量II.md b/problems/1049.最后一块石头的重量II.md index fcd3712a..f74600b1 100644 --- a/problems/1049.最后一块石头的重量II.md +++ b/problems/1049.最后一块石头的重量II.md @@ -178,7 +178,17 @@ class Solution { ``` Python： - +```python +class Solution: + def lastStoneWeightII(self, stones: List[int]) -> int: + sumweight = sum(stones) + target = sumweight // 2 + dp = [0] * 15001 + for i in range(len(stones)): + for j in range(target, stones[i] - 1, -1): + dp[j] = max(dp[j], dp[j - stones[i]] + stones[i]) + return sumweight - 2 * dp[target] +``` Go： From 659595f2b4d09d45d7301b728ac274b1cd52b39a Mon Sep 17 00:00:00 2001 From: NevS <1173325467@qq.com> Date: Mon, 31 May 2021 22:26:44 +0800 Subject: [PATCH 15/41] =?UTF-8?q?=E6=B7=BB=E5=8A=A0=200202.=E5=BF=AB?= =?UTF-8?q?=E4=B9=90=E6=95=B0=20go=E7=89=88?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- problems/0202.快乐数.md | 18 ++++++++++++++++++ 1 file changed, 18 insertions(+) diff --git a/problems/0202.快乐数.md b/problems/0202.快乐数.md index c07405ec..396231fe 100644 --- a/problems/0202.快乐数.md +++ b/problems/0202.快乐数.md @@ -111,6 +111,24 @@ Python： Go： +```go +func isHappy(n int) bool { + m := make(map[int]bool) + for n != 1 && !m[n] { + n, m[n] = getSum(n), true + } + return n == 1 +} + +func getSum(n int) int { + sum := 0 + for n > 0 { + sum += (n % 10) * (n % 10) + n = n / 10 + } + return sum +} +``` javaScript: From 605b9159de96de727cf4592144783c6d203f6fbe Mon Sep 17 00:00:00 2001 From: LiangDazhu <42199191+LiangDazhu@users.noreply.github.com> Date: Mon, 31 May 2021 22:49:40 +0800 Subject: [PATCH 16/41] =?UTF-8?q?Update=200494.=E7=9B=AE=E6=A0=87=E5=92=8C?= =?UTF-8?q?.md?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Added python version code --- problems/0494.目标和.md | 16 ++++++++++++++-- 1 file changed, 14 insertions(+), 2 deletions(-) diff --git a/problems/0494.目标和.md b/problems/0494.目标和.md index a9ddc768..c772a09d 100644 --- a/problems/0494.目标和.md +++ b/problems/0494.目标和.md @@ -150,7 +150,7 @@ dp[j] 表示：填满j（包括j）这么大容积的包，有dp[i]种方法 有哪些来源可以推出dp[j]呢？ -不考虑nums[i]的情况下，填满容量为j - nums[i]的背包，有dp[j - nums[i]]中方法。 +不考虑nums[i]的情况下，填满容量为j - nums[i]的背包，有dp[j - nums[i]]种方法。 那么只要搞到nums[i]的话，凑成dp[j]就有dp[j - nums[i]] 种方法。 @@ -261,7 +261,19 @@ class Solution { ``` Python： - +```python +class Solution: + def findTargetSumWays(self, nums: List[int], target: int) -> int: + sumValue = sum(nums) + if target > sumValue or (sumValue + target) % 2 == 1: return 0 + bagSize = (sumValue + target) // 2 + dp = [0] * (bagSize + 1) + dp[0] = 1 + for i in range(len(nums)): + for j in range(bagSize, nums[i] - 1, -1): + dp[j] += dp[j - nums[i]] + return dp[bagSize] +``` Go： From 425f407d6c66854446a1a2654bc1639171aee172 Mon Sep 17 00:00:00 2001 From: Baturu <45113401+z80160280@users.noreply.github.com> Date: Mon, 31 May 2021 11:20:40 -0700 Subject: [PATCH 17/41] =?UTF-8?q?Update=200024.=E4=B8=A4=E4=B8=A4=E4=BA=A4?= =?UTF-8?q?=E6=8D=A2=E9=93=BE=E8=A1=A8=E4=B8=AD=E7=9A=84=E8=8A=82=E7=82=B9?= =?UTF-8?q?.md?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- problems/0024.两两交换链表中的节点.md | 17 +++++++++++++++++ 1 file changed, 17 insertions(+) diff --git a/problems/0024.两两交换链表中的节点.md b/problems/0024.两两交换链表中的节点.md index 643f6055..59ded523 100644 --- a/problems/0024.两两交换链表中的节点.md +++ b/problems/0024.两两交换链表中的节点.md @@ -129,6 +129,23 @@ class Solution { ``` Python： +```python +class Solution: + def swapPairs(self, head: ListNode) -> ListNode: + dummy = ListNode(0) #设置一个虚拟头结点 + dummy.next = head + cur = dummy + while cur.next and cur.next.next: + tmp = cur.next #记录临时节点 + tmp1 = cur.next.next.next #记录临时节点 + + cur.next = cur.next.next #步骤一 + cur.next.next = tmp #步骤二 + cur.next.next.next = tmp1 #步骤三 + + cur = cur.next.next #cur移动两位，准备下一轮交换 + return dummy.next +``` Go： ```go From e5b81df01cdc6588710edb4bf7a88de6cc8a8da8 Mon Sep 17 00:00:00 2001 From: Yang Date: Mon, 31 May 2021 16:43:45 -0400 Subject: [PATCH 18/41] =?UTF-8?q?Update=200452.=E7=94=A8=E6=9C=80=E5=B0=91?= =?UTF-8?q?=E6=95=B0=E9=87=8F=E7=9A=84=E7=AE=AD=E5=BC=95=E7=88=86=E6=B0=94?= =?UTF-8?q?=E7=90=83.md?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Java code: - Fix an error in sorting (simplified as well) - Add checking for boundary condition --- problems/0452.用最少数量的箭引爆气球.md | 12 ++---------- 1 file changed, 2 insertions(+), 10 deletions(-) diff --git a/problems/0452.用最少数量的箭引爆气球.md b/problems/0452.用最少数量的箭引爆气球.md index a8b55ca9..9b0cc925 100644 --- a/problems/0452.用最少数量的箭引爆气球.md +++ b/problems/0452.用最少数量的箭引爆气球.md @@ -142,16 +142,8 @@ Java： ```java class Solution { public int findMinArrowShots(int[][] points) { - Arrays.sort(points, new Comparator() { - @Override - public int compare(int[] o1, int[] o2) { - if (o1[0] != o2[0]) { - return Integer.compare(o1[0],o2[0]); - } else { - return Integer.compare(o1[0],o2[0]); - } - } - }); + if (points.length == 0) return 0; + Arrays.sort(points, (o1, o2) -> Integer.compare(o1[0], o2[0])); int count = 1; for (int i = 1; i < points.length; i++) { From 72b2521873136f8f45648c185fd463f976f586ca Mon Sep 17 00:00:00 2001 From: fusunx <1102654482@qq.com> Date: Tue, 1 Jun 2021 08:15:47 +0800 Subject: [PATCH 19/41] =?UTF-8?q?1005.K=E6=AC=A1=E5=8F=96=E5=8F=8D.md=20Ja?= =?UTF-8?q?vascript?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- ...1005.K次取反后最大化的数组和.md | 22 +++++++++++++++++++ 1 file changed, 22 insertions(+) diff --git a/problems/1005.K次取反后最大化的数组和.md b/problems/1005.K次取反后最大化的数组和.md index 43282f25..e57e26ad 100644 --- a/problems/1005.K次取反后最大化的数组和.md +++ b/problems/1005.K次取反后最大化的数组和.md @@ -140,7 +140,29 @@ class Solution: Go： +Javascript: +```Javascript +var largestSumAfterKNegations = function(nums, k) { + nums.sort((a, b) => { + return Math.abs(b) - Math.abs(a) + }) + for(let i = 0; i < nums.length; i++) { + if(nums[i] < 0 && k > 0) { + nums[i] *= -1 + k-- + } + } + if(k > 0 && k % 2 === 1) { + nums[nums.length - 1] *= -1 + } + k = 0 + + return nums.reduce((a, b) => { + return a + b + }) +}; +``` ----------------------- * 作者微信：[程序员Carl](https://mp.weixin.qq.com/s/b66DFkOp8OOxdZC_xLZxfw) From 7a0d134d6e96541deb2fe4757743aed4c3ecd94e Mon Sep 17 00:00:00 2001 From: Baturu <45113401+z80160280@users.noreply.github.com> Date: Mon, 31 May 2021 18:31:10 -0700 Subject: [PATCH 20/41] =?UTF-8?q?Update=200242.=E6=9C=89=E6=95=88=E7=9A=84?= =?UTF-8?q?=E5=AD=97=E6=AF=8D=E5=BC=82=E4=BD=8D=E8=AF=8D.md?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- problems/0242.有效的字母异位词.md | 17 ++++++++++++++++- 1 file changed, 16 insertions(+), 1 deletion(-) diff --git a/problems/0242.有效的字母异位词.md b/problems/0242.有效的字母异位词.md index 6a6faf63..ba942f70 100644 --- a/problems/0242.有效的字母异位词.md +++ b/problems/0242.有效的字母异位词.md @@ -113,7 +113,22 @@ class Solution { ``` Python： - +```python +class Solution: + def isAnagram(self, s: str, t: str) -> bool: + record = [0] * 26 + for i in range(len(s)): + #并不需要记住字符a的ASCII，只要求出一个相对数值就可以了 + record[ord(s[i]) - ord("a")] += 1 + print(record) + for i in range(len(t)): + record[ord(t[i]) - ord("a")] -= 1 + for i in range(26): + if record[i] != 0: + #record数组如果有的元素不为零0，说明字符串s和t 一定是谁多了字符或者谁少了字符。 + return False + return True +``` Go： ```go From 4fc751affb0fba096c9263256555d59aa82615aa Mon Sep 17 00:00:00 2001 From: Baturu <45113401+z80160280@users.noreply.github.com> Date: Mon, 31 May 2021 18:42:19 -0700 Subject: [PATCH 21/41] =?UTF-8?q?Update=200202.=E5=BF=AB=E4=B9=90=E6=95=B0?= =?UTF-8?q?.md?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- problems/0202.快乐数.md | 24 +++++++++++++++++++++++- 1 file changed, 23 insertions(+), 1 deletion(-) diff --git a/problems/0202.快乐数.md b/problems/0202.快乐数.md index c07405ec..999e7d52 100644 --- a/problems/0202.快乐数.md +++ b/problems/0202.快乐数.md @@ -108,7 +108,29 @@ class Solution { ``` Python： - +```python +class Solution: + def isHappy(self, n: int) -> bool: + set_ = set() + while 1: + sum_ = self.getSum(n) + if sum_ == 1: + return True + #如果这个sum曾经出现过，说明已经陷入了无限循环了，立刻return false + if sum_ in set_: + return False + else: + set_.add(sum_) + n = sum_ + + #取数值各个位上的单数之和 + def getSum(self, n): + sum_ = 0 + while n > 0: + sum_ += (n%10) * (n%10) + n //= 10 + return sum_ +``` Go： From be0ef14cef18a6aeae95872c82dca0221d16f76b Mon Sep 17 00:00:00 2001 From: "qingyi.liu" Date: Tue, 1 Jun 2021 12:01:24 +0800 Subject: [PATCH 22/41] =?UTF-8?q?=E6=B7=BB=E5=8A=A0=20101.=20=E5=AF=B9?= =?UTF-8?q?=E7=A7=B0=E4=BA=8C=E5=8F=89=E6=A0=91=20go=E7=89=88=E6=9C=AC?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- problems/0101.对称二叉树.md | 48 ++++++++++++++++++++++++++++++++ 1 file changed, 48 insertions(+) diff --git a/problems/0101.对称二叉树.md b/problems/0101.对称二叉树.md index d8797d30..b58cef2e 100644 --- a/problems/0101.对称二叉树.md +++ b/problems/0101.对称二叉树.md @@ -363,6 +363,54 @@ Python： Go： +```go +/** + * Definition for a binary tree node. + * type TreeNode struct { + * Val int + * Left *TreeNode + * Right *TreeNode + * } + */ +// 递归 +func defs(left *TreeNode, right *TreeNode) bool { + if left == nil && right == nil { + return true; + }; + if left == nil || right == nil { + return false; + }; + if left.Val != right.Val { + return false; + } + return defs(left.Left, right.Right) && defs(right.Left, left.Right); +} +func isSymmetric(root *TreeNode) bool { + return defs(root.Left, root.Right); +} + +// 迭代 +func isSymmetric(root *TreeNode) bool { + var queue []*TreeNode; + if root != nil { + queue = append(queue, root.Left, root.Right); + } + for len(queue) > 0 { + left := queue[0]; + right := queue[1]; + queue = queue[2:]; + if left == nil && right == nil { + continue; + } + if left == nil || right == nil || left.Val != right.Val { + return false; + }; + queue = append(queue, left.Left, right.Right, right.Left, left.Right); + } + return true; +} +``` + JavaScript ```javascript From 0ddb3430986065f6a248c7936c3351544615161d Mon Sep 17 00:00:00 2001 From: "qingyi.liu" Date: Tue, 1 Jun 2021 12:22:46 +0800 Subject: [PATCH 23/41] =?UTF-8?q?=E6=B7=BB=E5=8A=A0=20104.=E4=BA=8C?= =?UTF-8?q?=E5=8F=89=E6=A0=91=E7=9A=84=E6=9C=80=E5=A4=A7=E6=B7=B1=E5=BA=A6?= =?UTF-8?q?=20go=E7=89=88=E6=9C=AC?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- problems/0104.二叉树的最大深度.md | 49 +++++++++++++++++++++++ 1 file changed, 49 insertions(+) diff --git a/problems/0104.二叉树的最大深度.md b/problems/0104.二叉树的最大深度.md index 756afb68..5f0fe411 100644 --- a/problems/0104.二叉树的最大深度.md +++ b/problems/0104.二叉树的最大深度.md @@ -284,6 +284,55 @@ Python： Go： +```go +/** + * Definition for a binary tree node. + * type TreeNode struct { + * Val int + * Left *TreeNode + * Right *TreeNode + * } + */ +func max (a, b int) int { + if a > b { + return a; + } + return b; +} +// 递归 +func maxDepth(root *TreeNode) int { + if root == nil { + return 0; + } + return max(maxDepth(root.Left), maxDepth(root.Right)) + 1; +} + +// 遍历 +func maxDepth(root *TreeNode) int { + levl := 0; + queue := make([]*TreeNode, 0); + if root != nil { + queue = append(queue, root); + } + for l := len(queue); l > 0; { + for ;l > 0;l-- { + node := queue[0]; + if node.Left != nil { + queue = append(queue, node.Left); + } + if node.Right != nil { + queue = append(queue, node.Right); + } + queue = queue[1:]; + } + levl++; + l = len(queue); + } + return levl; +} + +``` + JavaScript ```javascript From 51edb80d7c8771b0b9af932a577daeb658efd100 Mon Sep 17 00:00:00 2001 From: "qingyi.liu" Date: Tue, 1 Jun 2021 14:20:54 +0800 Subject: [PATCH 24/41] =?UTF-8?q?=E6=B7=BB=E5=8A=A0=20111.=E4=BA=8C?= =?UTF-8?q?=E5=8F=89=E6=A0=91=E7=9A=84=E6=9C=80=E5=B0=8F=E6=B7=B1=E5=BA=A6?= =?UTF-8?q?=20go=E7=89=88=E6=9C=AC?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- problems/0111.二叉树的最小深度.md | 58 +++++++++++++++++++++++ 1 file changed, 58 insertions(+) diff --git a/problems/0111.二叉树的最小深度.md b/problems/0111.二叉树的最小深度.md index 8ee15eac..48795722 100644 --- a/problems/0111.二叉树的最小深度.md +++ b/problems/0111.二叉树的最小深度.md @@ -301,6 +301,64 @@ class Solution: Go： +```go +/** + * Definition for a binary tree node. + * type TreeNode struct { + * Val int + * Left *TreeNode + * Right *TreeNode + * } + */ +func min(a, b int) int { + if a < b { + return a; + } + return b; +} +// 递归 +func minDepth(root *TreeNode) int { + if root == nil { + return 0; + } + if root.Left == nil && root.Right != nil { + return 1 + minDepth(root.Right); + } + if root.Right == nil && root.Left != nil { + return 1 + minDepth(root.Left); + } + return min(minDepth(root.Left), minDepth(root.Right)) + 1; +} + +// 迭代 + +func minDepth(root *TreeNode) int { + dep := 0; + queue := make([]*TreeNode, 0); + if root != nil { + queue = append(queue, root); + } + for l := len(queue); l > 0; { + dep++; + for ; l > 0; l-- { + node := queue[0]; + if node.Left == nil && node.Right == nil { + return dep; + } + if node.Left != nil { + queue = append(queue, node.Left); + } + if node.Right != nil { + queue = append(queue, node.Right); + } + queue = queue[1:]; + } + l = len(queue); + } + return dep; +} +``` + JavaScript: From ea88604bfdf249d686e1aba4a26795a35a57dcc8 Mon Sep 17 00:00:00 2001 From: Baturu <45113401+z80160280@users.noreply.github.com> Date: Tue, 1 Jun 2021 02:44:13 -0700 Subject: [PATCH 25/41] =?UTF-8?q?Update=200459.=E9=87=8D=E5=A4=8D=E7=9A=84?= =?UTF-8?q?=E5=AD=90=E5=AD=97=E7=AC=A6=E4=B8=B2.md?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- problems/0459.重复的子字符串.md | 49 ++++++++++++++++++++++++++ 1 file changed, 49 insertions(+) diff --git a/problems/0459.重复的子字符串.md b/problems/0459.重复的子字符串.md index d9dfc62c..51a903ef 100644 --- a/problems/0459.重复的子字符串.md +++ b/problems/0459.重复的子字符串.md @@ -184,6 +184,55 @@ class Solution { Python： +这里使用了前缀表统一减一的实现方式 + +```python +class Solution: + def repeatedSubstringPattern(self, s: str) -> bool: + if len(s) == 0: + return False + nxt = [0] * len(s) + self.getNext(nxt, s) + if nxt[-1] != -1 and len(s) % (len(s) - (nxt[-1] + 1)) == 0: + return True + return False + + def getNext(self, nxt, s): + nxt[0] = -1 + j = -1 + for i in range(1, len(s)): + while j >= 0 and s[i] != s[j+1]: + j = nxt[j] + if s[i] == s[j+1]: + j += 1 + nxt[i] = j + return nxt +``` + +前缀表（不减一）的代码实现 + +```python +class Solution: + def repeatedSubstringPattern(self, s: str) -> bool: + if len(s) == 0: + return False + nxt = [0] * len(s) + self.getNext(nxt, s) + if nxt[-1] != 0 and len(s) % (len(s) - nxt[-1]) == 0: + return True + return False + + def getNext(self, nxt, s): + nxt[0] = 0 + j = 0 + for i in range(1, len(s)): + while j > 0 and s[i] != s[j]: + j = nxt[j - 1] + if s[i] == s[j]: + j += 1 + nxt[i] = j + return nxt +``` Go： From 3362183d8446e551f0361ead95dca6bec8b7411a Mon Sep 17 00:00:00 2001 From: boom-jumper <56831966+boom-jumper@users.noreply.github.com> Date: Tue, 1 Jun 2021 18:08:16 +0800 Subject: [PATCH 26/41] =?UTF-8?q?=E6=B7=BB=E5=8A=A00347=E5=89=8DK=E4=B8=AA?= =?UTF-8?q?=E9=AB=98=E9=A2=91=E5=85=83=E7=B4=A0=20python3=20=E7=89=88?= =?UTF-8?q?=E6=9C=AC?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- problems/0347.前K个高频元素.md | 57 ++++++++++++++++++++++++++++ 1 file changed, 57 insertions(+) diff --git a/problems/0347.前K个高频元素.md b/problems/0347.前K个高频元素.md index 841584b4..29963b48 100644 --- a/problems/0347.前K个高频元素.md +++ b/problems/0347.前K个高频元素.md @@ -162,6 +162,63 @@ class Solution { Python： +```python +class Solution: + def sift(self, alist, low, high): + '''小根堆构建''' + i = low + j = 2 * i + 1 + tmp = alist[low] + while j <= high: + if j + 1 <= high and alist[j+1] <= alist[j]: + j += 1 + if alist[j] < tmp: + alist[i] = alist[j] + i = j + j = 2 * i + 1 + else: + alist[i] = tmp + break + else: + alist[i] = tmp + + + def topK(self, nums, k): + # 建立小根堆 + heap = nums[:k] + for i in range((k-2)//2, -1, -1): + self.sift(heap, i, k-1) + + # 把后续的k到len(nums)填充到小根堆里 + for i in range(k, len(nums)): + if nums[i] >= heap[0]: + heap[0] = nums[i] + self.sift(heap, 0, k-1) + + # 排序 + for i in range(k-1, -1, -1): + heap[0], heap[i]= heap[i], heap[0] + self.sift(heap, 0, i-1) + return heap + + def topKFrequent(self, nums: List[int], k: int) -> List[int]: + dict1 = dict() + for val in nums: + if val not in dict1: + dict1[val] = 1 + else: + dict1[val] += 1 + res = list() + ind = list() + for item in dict1: + res.append([dict1[item], item]) + result = list() + heap = self.topK(res, k) + print(heap) + for val in heap: + result.append(val[1]) + return result +``` Go： From d9e4b337243d51e39bf378737c8c2eac600de3d8 Mon Sep 17 00:00:00 2001 From: Baturu <45113401+z80160280@users.noreply.github.com> Date: Tue, 1 Jun 2021 03:47:40 -0700 Subject: [PATCH 27/41] =?UTF-8?q?Update=200239.=E6=BB=91=E5=8A=A8=E7=AA=97?= =?UTF-8?q?=E5=8F=A3=E6=9C=80=E5=A4=A7=E5=80=BC.md?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- problems/0239.滑动窗口最大值.md | 35 ++++++++++++++++++++++++++ 1 file changed, 35 insertions(+) diff --git a/problems/0239.滑动窗口最大值.md b/problems/0239.滑动窗口最大值.md index ed17157a..47383a47 100644 --- a/problems/0239.滑动窗口最大值.md +++ b/problems/0239.滑动窗口最大值.md @@ -263,6 +263,41 @@ class Solution { ``` Python： +```python +class MyQueue: #单调队列（从大到小 + def __init__(self): + self.queue = [] #使用list来实现单调队列 + + #每次弹出的时候，比较当前要弹出的数值是否等于队列出口元素的数值，如果相等则弹出。 + #同时pop之前判断队列当前是否为空。 + def pop(self, value): + if self.queue and value == self.queue[0]: + self.queue.pop(0)#list.pop()时间复杂度为O(n),这里可以使用collections.deque() + + #如果push的数值大于入口元素的数值，那么就将队列后端的数值弹出，直到push的数值小于等于队列入口元素的数值为止。 + #这样就保持了队列里的数值是单调从大到小的了。 + def push(self, value): + while self.queue and value > self.queue[-1]: + self.queue.pop() + self.queue.append(value) + + #查询当前队列里的最大值 直接返回队列前端也就是front就可以了。 + def front(self): + return self.queue[0] + +class Solution: + def maxSlidingWindow(self, nums: List[int], k: int) -> List[int]: + que = MyQueue() + result = [] + for i in range(k): #先将前k的元素放进队列 + que.push(nums[i]) + result.append(que.front()) #result 记录前k的元素的最大值 + for i in range(k, len(nums)): + que.pop(nums[i - k]) #滑动窗口移除最前面元素 + que.push(nums[i]) #滑动窗口前加入最后面的元素 + result.append(que.front()) #记录对应的最大值 + return result +``` Go： From 9219242b3af749a96efbbaf7d8ea5089a36ba7fe Mon Sep 17 00:00:00 2001 From: NevS <1173325467@qq.com> Date: Tue, 1 Jun 2021 20:34:57 +0800 Subject: [PATCH 28/41] =?UTF-8?q?=E6=B7=BB=E5=8A=A0=200001.=E4=B8=A4?= =?UTF-8?q?=E6=95=B0=E4=B9=8B=E5=92=8C=20go=E7=89=88?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 使用map方式解题，降低时间复杂度 --- problems/0001.两数之和.md | 14 ++++++++++++++ 1 file changed, 14 insertions(+) diff --git a/problems/0001.两数之和.md b/problems/0001.两数之和.md index 77318294..3d0674ce 100644 --- a/problems/0001.两数之和.md +++ b/problems/0001.两数之和.md @@ -134,6 +134,20 @@ func twoSum(nums []int, target int) []int { } return []int{} } + +```go +// 使用map方式解题，降低时间复杂度 +func twoSum(nums []int, target int) []int { + m := make(map[int]int) + for index, val := range nums { + if preIndex, ok := m[target-val]; ok { + return []int{preIndex, index} + } else { + m[val] = index + } + } + return []int{} +} ``` Rust From 36626386c329d75524843fab42f740e548578173 Mon Sep 17 00:00:00 2001 From: NevS <1173325467@qq.com> Date: Tue, 1 Jun 2021 20:35:55 +0800 Subject: [PATCH 29/41] =?UTF-8?q?=E6=9B=B4=E6=94=B9=200001.=E4=B8=A4?= =?UTF-8?q?=E6=95=B0=E4=B9=8B=E5=92=8C=20=E6=A0=BC=E5=BC=8F?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- problems/0001.两数之和.md | 1 + 1 file changed, 1 insertion(+) diff --git a/problems/0001.两数之和.md b/problems/0001.两数之和.md index 3d0674ce..4a1a987f 100644 --- a/problems/0001.两数之和.md +++ b/problems/0001.两数之和.md @@ -134,6 +134,7 @@ func twoSum(nums []int, target int) []int { } return []int{} } +``` ```go // 使用map方式解题，降低时间复杂度 From ce970df5ffdb2e428b4ec2417e2bbccdc9371a31 Mon Sep 17 00:00:00 2001 From: NevS <1173325467@qq.com> Date: Tue, 1 Jun 2021 23:43:02 +0800 Subject: [PATCH 30/41] =?UTF-8?q?=E6=B7=BB=E5=8A=A0=200454.=E5=9B=9B?= =?UTF-8?q?=E6=95=B0=E7=9B=B8=E5=8A=A0II=20go=E7=89=88=E6=9C=AC?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- problems/0454.四数相加II.md | 17 +++++++++++++++++ 1 file changed, 17 insertions(+) diff --git a/problems/0454.四数相加II.md b/problems/0454.四数相加II.md index 2c648f58..5291060c 100644 --- a/problems/0454.四数相加II.md +++ b/problems/0454.四数相加II.md @@ -154,6 +154,23 @@ class Solution(object): Go： +```go +func fourSumCount(nums1 []int, nums2 []int, nums3 []int, nums4 []int) int { + m := make(map[int]int) + count := 0 + for _, v1 := range nums1 { + for _, v2 := range nums2 { + m[v1+v2]++ + } + } + for _, v3 := range nums3 { + for _, v4 := range nums4 { + count += m[-v3-v4] + } + } + return count +} +``` javaScript: From 67313906d16f8cf0e613968bf0f9b8031a273cdd Mon Sep 17 00:00:00 2001 From: Yang Date: Tue, 1 Jun 2021 14:41:22 -0400 Subject: [PATCH 31/41] =?UTF-8?q?Update=200056.=E5=90=88=E5=B9=B6=E5=8C=BA?= =?UTF-8?q?=E9=97=B4.md?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Update Java solution. For sorting, no need to compare the second element in an interval. --- problems/0056.合并区间.md | 6 +----- 1 file changed, 1 insertion(+), 5 deletions(-) diff --git a/problems/0056.合并区间.md b/problems/0056.合并区间.md index eb8e7bff..f42fced7 100644 --- a/problems/0056.合并区间.md +++ b/problems/0056.合并区间.md @@ -144,11 +144,7 @@ class Solution { Arrays.sort(intervals, new Comparator() { @Override public int compare(int[] o1, int[] o2) { - if (o1[0] != o2[0]) { - return Integer.compare(o1[0],o2[0]); - } else { - return Integer.compare(o1[1],o2[1]); - } + return Integer.compare(o1[0], o2[0]); } }); From 838e290312af9218c62630a18022087205c8a2bc Mon Sep 17 00:00:00 2001 From: Yang Date: Tue, 1 Jun 2021 14:46:19 -0400 Subject: [PATCH 32/41] =?UTF-8?q?Update=200056.=E5=90=88=E5=B9=B6=E5=8C=BA?= =?UTF-8?q?=E9=97=B4.md?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Simplify sorting --- problems/0056.合并区间.md | 7 +------ 1 file changed, 1 insertion(+), 6 deletions(-) diff --git a/problems/0056.合并区间.md b/problems/0056.合并区间.md index f42fced7..43ff447d 100644 --- a/problems/0056.合并区间.md +++ b/problems/0056.合并区间.md @@ -141,12 +141,7 @@ Java： class Solution { public int[][] merge(int[][] intervals) { List res = new LinkedList<>(); - Arrays.sort(intervals, new Comparator() { - @Override - public int compare(int[] o1, int[] o2) { - return Integer.compare(o1[0], o2[0]); - } - }); + Arrays.sort(intervals, (o1, o2) -> o1[0] - o2[0]); int start = intervals[0][0]; for (int i = 1; i < intervals.length; i++) { From f4736c7dd2fb5ce75864dc34baf5e4bf212c16d4 Mon Sep 17 00:00:00 2001 From: Yang Date: Tue, 1 Jun 2021 14:48:52 -0400 Subject: [PATCH 33/41] Improve comparison --- problems/0056.合并区间.md | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/problems/0056.合并区间.md b/problems/0056.合并区间.md index 43ff447d..d4ffc554 100644 --- a/problems/0056.合并区间.md +++ b/problems/0056.合并区间.md @@ -141,7 +141,7 @@ Java： class Solution { public int[][] merge(int[][] intervals) { List res = new LinkedList<>(); - Arrays.sort(intervals, (o1, o2) -> o1[0] - o2[0]); + Arrays.sort(intervals, (o1, o2) -> Integer.compare(o1[0], o2[0])); int start = intervals[0][0]; for (int i = 1; i < intervals.length; i++) { From bb5cfa68b2a20bc3609b56cd65d2542630c86f37 Mon Sep 17 00:00:00 2001 From: "Neil.Liu" <88214924@qq.com> Date: Wed, 2 Jun 2021 10:15:47 +0800 Subject: [PATCH 34/41] =?UTF-8?q?=E6=B7=BB=E5=8A=A00151.=E7=BF=BB=E8=BD=AC?= =?UTF-8?q?=E5=AD=97=E7=AC=A6=E4=B8=B2=E9=87=8C=E7=9A=84=E5=8D=95=E8=AF=8D?= =?UTF-8?q?Go=E7=89=88=E6=9C=AC?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- problems/0151.翻转字符串里的单词.md | 56 +++++++++++++++++++- 1 file changed, 54 insertions(+), 2 deletions(-) diff --git a/problems/0151.翻转字符串里的单词.md b/problems/0151.翻转字符串里的单词.md index 512360fe..63499b71 100644 --- a/problems/0151.翻转字符串里的单词.md +++ b/problems/0151.翻转字符串里的单词.md @@ -318,9 +318,61 @@ class Solution { Python： - Go： +```go +import ( + "fmt" +) + +func reverseWords(s string) string { + //1.使用双指针删除冗余的空格 + slowIndex, fastIndex := 0, 0 + b := []byte(s) + //删除头部冗余空格 + for len(b) > 0 && fastIndex < len(b) && b[fastIndex] == ' ' { + fastIndex++ + } + //删除单词间冗余空格 + for ; fastIndex < len(b); fastIndex++ { + if fastIndex-1 > 0 && b[fastIndex-1] == b[fastIndex] && b[fastIndex] == ' ' { + continue + } + b[slowIndex] = b[fastIndex] + slowIndex++ + } + //删除尾部冗余空格 + if slowIndex-1 > 0 && b[slowIndex-1] == ' ' { + b = b[:slowIndex-1] + } else { + b = b[:slowIndex] + } + //2.反转整个字符串 + reverse(&b, 0, len(b)-1) + //3.反转单个单词 i单词开始位置，j单词结束位置 + i := 0 + for i < len(b) { + j := i + for ; j < len(b) && b[j] != ' '; j++ { + } + reverse(&b, i, j-1) + i = j + i++ + } + return string(b) +} + +func reverse(b *[]byte, left, right int) { + for left < right { + (*b)[left], (*b)[right] = (*b)[right], (*b)[left] + left++ + right-- + } +} +``` + + + @@ -328,4 +380,4 @@ Go： * 作者微信：[程序员Carl](https://mp.weixin.qq.com/s/b66DFkOp8OOxdZC_xLZxfw) * B站视频：[代码随想录](https://space.bilibili.com/525438321) * 知识星球：[代码随想录](https://mp.weixin.qq.com/s/QVF6upVMSbgvZy8lHZS3CQ) -
+
\ No newline at end of file From fae5373477b50d259c94c08dcef1ce6254081491 Mon Sep 17 00:00:00 2001 From: "Neil.Liu" <88214924@qq.com> Date: Wed, 2 Jun 2021 10:25:09 +0800 Subject: [PATCH 35/41] =?UTF-8?q?=E6=B7=BB=E5=8A=A0=E5=89=91=E6=8C=87Offer?= =?UTF-8?q?58-II.=E5=B7=A6=E6=97=8B=E8=BD=AC=E5=AD=97=E7=AC=A6=E4=B8=B2Go?= =?UTF-8?q?=E7=89=88=E6=9C=AC?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- .../剑指Offer58-II.左旋转字符串.md | 28 +++++++++++++++++-- 1 file changed, 25 insertions(+), 3 deletions(-) diff --git a/problems/剑指Offer58-II.左旋转字符串.md b/problems/剑指Offer58-II.左旋转字符串.md index 648546c1..39c8382c 100644 --- a/problems/剑指Offer58-II.左旋转字符串.md +++ b/problems/剑指Offer58-II.左旋转字符串.md @@ -23,7 +23,7 @@ https://leetcode-cn.com/problems/zuo-xuan-zhuan-zi-fu-chuan-lcof/ 示例 2： 输入: s = "lrloseumgh", k = 6 输出: "umghlrlose" -  + 限制： 1 <= k < s.length <= 10000 @@ -119,9 +119,31 @@ class Solution { ``` Python： - Go： +```go +func reverseLeftWords(s string, n int) string { + b := []byte(s) + // 1. 反转前n个字符 + // 2. 反转第n到end字符 + // 3. 反转整个字符 + reverse(b, 0, n-1) + reverse(b, n, len(b)-1) + reverse(b, 0, len(b)-1) + return string(b) +} +// 切片是引用传递 +func reverse(b []byte, left, right int){ + for left < right{ + b[left], b[right] = b[right],b[left] + left++ + right-- + } +} +``` + + + @@ -129,4 +151,4 @@ Go： * 作者微信：[程序员Carl](https://mp.weixin.qq.com/s/b66DFkOp8OOxdZC_xLZxfw) * B站视频：[代码随想录](https://space.bilibili.com/525438321) * 知识星球：[代码随想录](https://mp.weixin.qq.com/s/QVF6upVMSbgvZy8lHZS3CQ) -
+
\ No newline at end of file From 9163ed6b65667e4c95a9ed2b26bd63a6a516fc9f Mon Sep 17 00:00:00 2001 From: zhangzw Date: Wed, 2 Jun 2021 11:49:59 +0800 Subject: [PATCH 36/41] =?UTF-8?q?=E6=B7=BB=E5=8A=A01049.=E6=9C=80=E5=90=8E?= =?UTF-8?q?=E4=B8=80=E5=9D=97=E7=9F=B3=E5=A4=B4=E7=9A=84=E9=87=8D=E9=87=8F?= =?UTF-8?q?II=20Go=E7=89=88=E6=9C=AC?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- .../1049.最后一块石头的重量II.md | 26 +++++++++++++++++++ 1 file changed, 26 insertions(+) diff --git a/problems/1049.最后一块石头的重量II.md b/problems/1049.最后一块石头的重量II.md index f74600b1..c09e476a 100644 --- a/problems/1049.最后一块石头的重量II.md +++ b/problems/1049.最后一块石头的重量II.md @@ -191,7 +191,33 @@ class Solution: ``` Go： +```go +func lastStoneWeightII(stones []int) int { + // 15001 = 30 * 1000 /2 +1 + dp := make([]int, 15001) + // 求target + sum := 0 + for _, v := range stones { + sum += v + } + target := sum / 2 + // 遍历顺序 + for i := 0; i < len(stones); i++ { + for j := target; j >= stones[i]; j-- { + // 推导公式 + dp[j] = max(dp[j], dp[j-stones[i]]+stones[i]) + } + } + return sum - 2 * dp[target] +} +func max(a, b int) int { + if a > b { + return a + } + return b +} +``` From 9f84671e690208a1b40debe15b1bfa624448f348 Mon Sep 17 00:00:00 2001 From: zhangzw Date: Wed, 2 Jun 2021 11:51:50 +0800 Subject: [PATCH 37/41] =?UTF-8?q?=E6=B7=BB=E5=8A=A00494.=E7=9B=AE=E6=A0=87?= =?UTF-8?q?=E5=92=8C=20Go=E7=89=88=E6=9C=AC?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- problems/0494.目标和.md | 30 +++++++++++++++++++++++++++++- 1 file changed, 29 insertions(+), 1 deletion(-) diff --git a/problems/0494.目标和.md b/problems/0494.目标和.md index c772a09d..c917ed5c 100644 --- a/problems/0494.目标和.md +++ b/problems/0494.目标和.md @@ -276,7 +276,35 @@ class Solution: ``` Go： - +```go +func findTargetSumWays(nums []int, target int) int { + sum := 0 + for _, v := range nums { + sum += v + } + if target > sum { + return 0 + } + if (sum+target)%2 == 1 { + return 0 + } + // 计算背包大小 + bag := (sum + target) / 2 + // 定义dp数组 + dp := make([]int, bag+1) + // 初始化 + dp[0] = 1 + // 遍历顺序 + for i := 0; i < len(nums); i++ { + for j := bag; j >= nums[i]; j-- { + //推导公式 + dp[j] += dp[j-nums[i]] + //fmt.Println(dp) + } + } + return dp[bag] +} +``` From 9707fbc521b16e79a43ef588e4f4a77454a30fdf Mon Sep 17 00:00:00 2001 From: Baturu <45113401+z80160280@users.noreply.github.com> Date: Wed, 2 Jun 2021 02:41:59 -0700 Subject: [PATCH 38/41] =?UTF-8?q?Update=200347.=E5=89=8DK=E4=B8=AA?= =?UTF-8?q?=E9=AB=98=E9=A2=91=E5=85=83=E7=B4=A0.md?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- problems/0347.前K个高频元素.md | 28 +++++++++++++++++++++++++++- 1 file changed, 27 insertions(+), 1 deletion(-) diff --git a/problems/0347.前K个高频元素.md b/problems/0347.前K个高频元素.md index 841584b4..71af618e 100644 --- a/problems/0347.前K个高频元素.md +++ b/problems/0347.前K个高频元素.md @@ -162,7 +162,33 @@ class Solution { Python： - +```python +#时间复杂度：O(nlogk) +#空间复杂度：O(n) +import heapq +class Solution: + def topKFrequent(self, nums: List[int], k: int) -> List[int]: + #要统计元素出现频率 + map_ = {} #nums[i]:对应出现的次数 + for i in range(len(nums)): + map_[nums[i]] = map_.get(nums[i], 0) + 1 + + #对频率排序 + #定义一个小顶堆，大小为k + pri_que = [] #小顶堆 + + #用固定大小为k的小顶堆，扫面所有频率的数值 + for key, freq in map_.items(): + heapq.heappush(pri_que, (freq, key)) + if len(pri_que) > k: #如果堆的大小大于了K，则队列弹出，保证堆的大小一直为k + heapq.heappop(pri_que) + + #找出前K个高频元素，因为小顶堆先弹出的是最小的，所以倒叙来输出到数组 + result = [0] * k + for i in range(k-1, -1, -1): + result[i] = heapq.heappop(pri_que)[1] + return result +``` Go： From 2a7c3cb87c2fbcefe1b1995cfa0d45ba7e857627 Mon Sep 17 00:00:00 2001 From: Baturu <45113401+z80160280@users.noreply.github.com> Date: Wed, 2 Jun 2021 03:09:05 -0700 Subject: [PATCH 39/41] =?UTF-8?q?Update=20=E4=BA=8C=E5=8F=89=E6=A0=91?= =?UTF-8?q?=E7=9A=84=E7=BB=9F=E4=B8=80=E8=BF=AD=E4=BB=A3=E6=B3=95.md?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- problems/二叉树的统一迭代法.md | 71 +++++++++++++++++++++++++ 1 file changed, 71 insertions(+) diff --git a/problems/二叉树的统一迭代法.md b/problems/二叉树的统一迭代法.md index dca5d3e3..dc79643d 100644 --- a/problems/二叉树的统一迭代法.md +++ b/problems/二叉树的统一迭代法.md @@ -239,7 +239,78 @@ Java： ``` Python： +> 迭代法前序遍历 +```python +class Solution: + def preorderTraversal(self, root: TreeNode) -> List[int]: + result = [] + st= [] + if root: + st.append(root) + while st: + node = st.pop() + if node != None: + if node.right: #右 + st.append(node.right) + if node.left: #左 + st.append(node.left) + st.append(node) #中 + st.append(None) + else: + node = st.pop() + result.append(node.val) + return result +``` + +> 迭代法中序遍历 +```python +class Solution: + def inorderTraversal(self, root: TreeNode) -> List[int]: + result = [] + st = [] + if root: + st.append(root) + while st: + node = st.pop() + if node != None: + if node.right: #添加右节点（空节点不入栈） + st.append(node.right) + + st.append(node) #添加中节点 + st.append(None) #中节点访问过，但是还没有处理，加入空节点做为标记。 + + if node.left: #添加左节点（空节点不入栈） + st.append(node.left) + else: #只有遇到空节点的时候，才将下一个节点放进结果集 + node = st.pop() #重新取出栈中元素 + result.append(node.val) #加入到结果集 + return result +``` + +> 迭代法后序遍历 +```python +class Solution: + def postorderTraversal(self, root: TreeNode) -> List[int]: + result = [] + st = [] + if root: + st.append(root) + while st: + node = st.pop() + if node != None: + st.append(node) #中 + st.append(None) + + if node.right: #右 + st.append(node.right) + if node.left: #左 + st.append(node.left) + else: + node = st.pop() + result.append(node.val) + return result +``` Go： > 前序遍历统一迭代法 From 045f3f98d6234e548c8b98edee911f2eb39b482f Mon Sep 17 00:00:00 2001 From: fusunx <1102654482@qq.com> Date: Wed, 2 Jun 2021 20:10:28 +0800 Subject: [PATCH 40/41] =?UTF-8?q?0134.=E5=8A=A0=E6=B2=B9=E7=AB=99.md=20Jav?= =?UTF-8?q?ascript?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- problems/0134.加油站.md | 21 +++++++++++++++++++++ 1 file changed, 21 insertions(+) diff --git a/problems/0134.加油站.md b/problems/0134.加油站.md index 5c3f70a8..dfed2d96 100644 --- a/problems/0134.加油站.md +++ b/problems/0134.加油站.md @@ -241,7 +241,28 @@ class Solution: Go： +Javascript: +```Javascript +var canCompleteCircuit = function(gas, cost) { + const gasLen = gas.length + let start = 0 + let curSum = 0 + let totalSum = 0 + for(let i = 0; i < gasLen; i++) { + curSum += gas[i] - cost[i] + totalSum += gas[i] - cost[i] + if(curSum < 0) { + curSum = 0 + start = i + 1 + } + } + + if(totalSum < 0) return -1 + + return start +}; +``` ----------------------- From bed3f0b09fc46f11d319f33225e78e7c12d5842b Mon Sep 17 00:00:00 2001 From: NevS <1173325467@qq.com> Date: Wed, 2 Jun 2021 20:11:11 +0800 Subject: [PATCH 41/41] =?UTF-8?q?=E6=B7=BB=E5=8A=A0=200383.=E8=B5=8E?= =?UTF-8?q?=E9=87=91=E4=BF=A1=20go=E7=89=88?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- problems/0383.赎金信.md | 15 +++++++++++++++ 1 file changed, 15 insertions(+) diff --git a/problems/0383.赎金信.md b/problems/0383.赎金信.md index fd8175db..23e2c5fd 100644 --- a/problems/0383.赎金信.md +++ b/problems/0383.赎金信.md @@ -166,6 +166,21 @@ class Solution(object): ``` Go： +```go +func canConstruct(ransomNote string, magazine string) bool { + record := make([]int, 26) + for _, v := range magazine { + record[v-'a']++ + } + for _, v := range ransomNote { + record[v-'a']-- + if record[v-'a'] < 0 { + return false + } + } + return true +} +``` javaScript: