From d0e032dc9be90d8f707c760847803e94ee85fd29 Mon Sep 17 00:00:00 2001 From: zjd <12321619+realpeanut@users.noreply.github.com> Date: Wed, 12 May 2021 10:59:58 +0800 Subject: [PATCH 01/37] =?UTF-8?q?Update=20=E4=BA=8C=E5=8F=89=E6=A0=91?= =?UTF-8?q?=E7=90=86=E8=AE=BA=E5=9F=BA=E7=A1=80.md?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- problems/二叉树理论基础.md | 12 +++++++++--- 1 file changed, 9 insertions(+), 3 deletions(-) diff --git a/problems/二叉树理论基础.md b/problems/二叉树理论基础.md index 726fc7a8..2230d404 100644 --- a/problems/二叉树理论基础.md +++ b/problems/二叉树理论基础.md @@ -46,7 +46,7 @@ ### 二叉搜索树 -前面介绍的书，都没有数值的，而二叉搜索树是有数值的了，**二叉搜索树是一个有序树**。 +前面介绍的树，都没有数值的，而二叉搜索树是有数值的了，**二叉搜索树是一个有序树**。 * 若它的左子树不空，则左子树上所有结点的值均小于它的根结点的值； @@ -164,7 +164,7 @@ struct TreeNode { 大家会发现二叉树的定义 和链表是差不多的，相对于链表 ，二叉树的节点里多了一个指针， 有两个指针，指向左右孩子. -这里要提醒大家要注意二叉树节点定义的书写方式。 +这里要提醒大家要注意二叉树节点定义的写方式。 **在现场面试的时候 面试官可能要求手写代码，所以数据结构的定义以及简单逻辑的代码一定要锻炼白纸写出来。** @@ -193,7 +193,13 @@ Python： Go： - +``` +type TreeNode struct { + Val int + Left *TreeNode + Right *TreeNode +} +``` From 309a1cf9ad9c1b0c62833d822d20531268b7b3e8 Mon Sep 17 00:00:00 2001 From: zjd <12321619+realpeanut@users.noreply.github.com> Date: Wed, 12 May 2021 11:11:52 +0800 Subject: [PATCH 02/37] =?UTF-8?q?Update=20=E4=BA=8C=E5=8F=89=E6=A0=91?= =?UTF-8?q?=E7=90=86=E8=AE=BA=E5=9F=BA=E7=A1=80.md?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- problems/二叉树理论基础.md | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/problems/二叉树理论基础.md b/problems/二叉树理论基础.md index 2230d404..60e65c69 100644 --- a/problems/二叉树理论基础.md +++ b/problems/二叉树理论基础.md @@ -164,7 +164,7 @@ struct TreeNode { 大家会发现二叉树的定义 和链表是差不多的，相对于链表 ，二叉树的节点里多了一个指针， 有两个指针，指向左右孩子. -这里要提醒大家要注意二叉树节点定义的写方式。 +这里要提醒大家要注意二叉树节点定义的书写方式。 **在现场面试的时候 面试官可能要求手写代码，所以数据结构的定义以及简单逻辑的代码一定要锻炼白纸写出来。** @@ -195,9 +195,9 @@ Python： Go： ``` type TreeNode struct { - Val int - Left *TreeNode - Right *TreeNode + Val int + Left *TreeNode + Right *TreeNode } ``` From 60c1908c4d89b3bc9c0c0ce5ab7acfe6100f4412 Mon Sep 17 00:00:00 2001 From: zjd <12321619+realpeanut@users.noreply.github.com> Date: Wed, 12 May 2021 11:40:40 +0800 Subject: [PATCH 03/37] =?UTF-8?q?=E4=BA=8C=E5=8F=89=E6=A0=91=E9=80=92?= =?UTF-8?q?=E5=BD=92=E9=81=8D=E5=8E=86=E5=A2=9E=E5=8A=A0golang=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/二叉树的递归遍历.md | 52 ++++++++++++++++++++++++++++ 1 file changed, 52 insertions(+) diff --git a/problems/二叉树的递归遍历.md b/problems/二叉树的递归遍历.md index 6c005191..bd3a9e1c 100644 --- a/problems/二叉树的递归遍历.md +++ b/problems/二叉树的递归遍历.md @@ -122,6 +122,58 @@ Python： Go： +前序遍历: +``` +func PreorderTraversal(root *TreeNode) (res []int) { + var traversal func(node *TreeNode) + traversal = func(node *TreeNode) { + if node == nil { + return + } + res = append(res,node.Val) + traversal(node.Left) + traversal(node.Right) + } + traversal(root) + return res +} + +``` +中序遍历: + +``` +func InorderTraversal(root *TreeNode) (res []int) { + var traversal func(node *TreeNode) + traversal = func(node *TreeNode) { + if node == nil { + return + } + traversal(node.Left) + res = append(res,node.Val) + traversal(node.Right) + } + traversal(root) + return res +} +``` +后序遍历: + +``` +func PostorderTraversal(root *TreeNode) (res []int) { + var traversal func(node *TreeNode) + traversal = func(node *TreeNode) { + if node == nil { + return + } + traversal(node.Left) + traversal(node.Right) + res = append(res,node.Val) + } + traversal(root) + return res +} +``` + From 08efaac9f722afa677a40b5d7509d18cd07994c9 Mon Sep 17 00:00:00 2001 From: zjd <12321619+realpeanut@users.noreply.github.com> Date: Wed, 12 May 2021 11:44:30 +0800 Subject: [PATCH 04/37] =?UTF-8?q?Update=20=E4=BA=8C=E5=8F=89=E6=A0=91?= =?UTF-8?q?=E7=9A=84=E9=80=92=E5=BD=92=E9=81=8D=E5=8E=86.md?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- problems/二叉树的递归遍历.md | 60 ++++++++++++++-------------- 1 file changed, 30 insertions(+), 30 deletions(-) diff --git a/problems/二叉树的递归遍历.md b/problems/二叉树的递归遍历.md index bd3a9e1c..02d4b060 100644 --- a/problems/二叉树的递归遍历.md +++ b/problems/二叉树的递归遍历.md @@ -125,17 +125,17 @@ Go： 前序遍历: ``` func PreorderTraversal(root *TreeNode) (res []int) { - var traversal func(node *TreeNode) - traversal = func(node *TreeNode) { - if node == nil { - return - } - res = append(res,node.Val) - traversal(node.Left) - traversal(node.Right) + var traversal func(node *TreeNode) + traversal = func(node *TreeNode) { + if node == nil { + return } - traversal(root) - return res + res = append(res,node.Val) + traversal(node.Left) + traversal(node.Right) + } + traversal(root) + return res } ``` @@ -143,34 +143,34 @@ func PreorderTraversal(root *TreeNode) (res []int) { ``` func InorderTraversal(root *TreeNode) (res []int) { - var traversal func(node *TreeNode) - traversal = func(node *TreeNode) { - if node == nil { - return - } - traversal(node.Left) - res = append(res,node.Val) - traversal(node.Right) + var traversal func(node *TreeNode) + traversal = func(node *TreeNode) { + if node == nil { + return } - traversal(root) - return res + traversal(node.Left) + res = append(res,node.Val) + traversal(node.Right) + } + traversal(root) + return res } ``` 后序遍历: ``` func PostorderTraversal(root *TreeNode) (res []int) { - var traversal func(node *TreeNode) - traversal = func(node *TreeNode) { - if node == nil { - return - } - traversal(node.Left) - traversal(node.Right) - res = append(res,node.Val) + var traversal func(node *TreeNode) + traversal = func(node *TreeNode) { + if node == nil { + return } - traversal(root) - return res + traversal(node.Left) + traversal(node.Right) + res = append(res,node.Val) + } + traversal(root) + return res } ``` From 259f16779a75661a082c7dae378c534c3a29146d Mon Sep 17 00:00:00 2001 From: Webary <813577991@qq.com> Date: Wed, 12 May 2021 13:22:46 +0800 Subject: [PATCH 05/37] =?UTF-8?q?=E6=B7=BB=E5=8A=A00020.=E6=9C=89=E6=95=88?= =?UTF-8?q?=E7=9A=84=E6=8B=AC=E5=8F=B7Python=E7=89=88=E6=9C=AC?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- problems/0020.有效的括号.md | 15 ++++++++++++++- 1 file changed, 14 insertions(+), 1 deletion(-) diff --git a/problems/0020.有效的括号.md b/problems/0020.有效的括号.md index e8784397..f2d78ade 100644 --- a/problems/0020.有效的括号.md +++ b/problems/0020.有效的括号.md @@ -141,7 +141,20 @@ Java： Python： - +```python3 +class Solution: + def isValid(self, s: str) -> bool: + stack = [] # 保存还未匹配的左括号 + mapping = {")": "(", "]": "[", "}": "{"} + for i in s: + if i in "([{": # 当前是左括号，则入栈 + stack.append(i) + elif stack and stack[-1] == mapping[i]: # 当前是配对的右括号则出栈 + stack.pop() + else: # 不是匹配的右括号或者没有左括号与之匹配，则返回false + return False + return stack == [] # 最后必须正好把左括号匹配完 +``` Go： From 1f609be3b329654b99194591b3e0c132b3d5ad58 Mon Sep 17 00:00:00 2001 From: Tiansheng Sui Date: Tue, 11 May 2021 23:38:24 -0700 Subject: [PATCH 06/37] =?UTF-8?q?=E6=B7=BB=E5=8A=A00704.=E4=BA=8C=E5=88=86?= =?UTF-8?q?=E6=9F=A5=E6=89=BEPython=E7=89=88=E6=9C=AC?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- problems/0704.二分查找.md | 16 ++++++++++++++++ 1 file changed, 16 insertions(+) diff --git a/problems/0704.二分查找.md b/problems/0704.二分查找.md index 9261e135..bb013d95 100644 --- a/problems/0704.二分查找.md +++ b/problems/0704.二分查找.md @@ -151,6 +151,22 @@ Java： Python： +```python3 +class Solution: + def search(self, nums: List[int], target: int) -> int: + left, right = 0, len(nums) - 1 + + while left <= right: + middle = (left + right) // 2 + + if nums[middle] < target: + left = middle + 1 + elif nums[middle] > target: + right = middle - 1 + else: + return middle + return -1 +``` Go： From 04bb63da12b4bd0ba9c38a4ca12e6334f1c155c7 Mon Sep 17 00:00:00 2001 From: X-shuffle <53906918+X-shuffle@users.noreply.github.com> Date: Wed, 12 May 2021 15:41:32 +0800 Subject: [PATCH 07/37] =?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 添加27. 移除元素 go版本 --- problems/0242.有效的字母异位词.md | 15 +++++++++++++-- 1 file changed, 13 insertions(+), 2 deletions(-) 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 9c492431..463a793f 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 @@ -91,8 +91,19 @@ Python： Go： - - +```go +func removeElement(nums []int, val int) int { + length:=len(nums) + res:=0 + for i:=0;i Date: Wed, 12 May 2021 15:44:55 +0800 Subject: [PATCH 08/37] =?UTF-8?q?Update=200027.=E7=A7=BB=E9=99=A4=E5=85=83?= =?UTF-8?q?=E7=B4=A0.md?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 添加0027.移除元素 go版本 --- problems/0027.移除元素.md | 14 +++++++++++++- 1 file changed, 13 insertions(+), 1 deletion(-) diff --git a/problems/0027.移除元素.md b/problems/0027.移除元素.md index 5cfdb68d..144cd5be 100644 --- a/problems/0027.移除元素.md +++ b/problems/0027.移除元素.md @@ -129,7 +129,19 @@ Python： Go： - +```go +func removeElement(nums []int, val int) int { + length:=len(nums) + res:=0 + for i:=0;i Date: Wed, 12 May 2021 15:48:38 +0800 Subject: [PATCH 09/37] =?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 添加0242.有效的字母异位词 go版本 --- problems/0242.有效的字母异位词.md | 26 ++++++++++++++++------- 1 file changed, 18 insertions(+), 8 deletions(-) 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 463a793f..be553c5a 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 @@ -92,16 +92,26 @@ Python： Go： ```go -func removeElement(nums []int, val int) int { - length:=len(nums) - res:=0 - for i:=0;i=0&&ok{ + exists[s[i]]=v+1 + }else{ + exists[s[i]]=1 } } - return res + for i:=0;i=1&&ok{ + exists[t[i]]=v-1 + }else{ + return false + } + } + return true } ``` From 612d400c36c28ea9917ac2b13b23f7fed7d73420 Mon Sep 17 00:00:00 2001 From: doo0301 Date: Wed, 12 May 2021 15:21:02 +0800 Subject: [PATCH 10/37] =?UTF-8?q?0102.=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.md=20=20Java?= 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 | 30 +++++++++++++++++++++++ 1 file changed, 30 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 cfbe09f3..8c34d415 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 @@ -419,6 +419,36 @@ public: Java： +```Java + +class Solution { + public List> resList=new ArrayList>(); + public List> levelOrder(TreeNode root) { + checkFun01(root,0); + + return resList; + } + + //递归方式 + public void checkFun01(TreeNode node,Integer deep){ + if(node==null) return; + deep++; + + if(resList.size() item=new ArrayList(); + resList.add(item); + } + resList.get(deep-1).add(node.val); + + + checkFun01(node.left,deep); + checkFun01(node.right,deep); + } + + +``` + Python： From a40b5094a93ed10bbec05e96354e570bc4267f19 Mon Sep 17 00:00:00 2001 From: HermanZzz Date: Wed, 12 May 2021 15:59:24 +0800 Subject: [PATCH 11/37] =?UTF-8?q?=E6=B7=BB=E5=8A=A00112.=E8=B7=AF=E5=BE=84?= =?UTF-8?q?=E6=80=BB=E5=92=8C=20JavaScript=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 | 31 +++++++++++++++++++++++++++++++ 1 file changed, 31 insertions(+) diff --git a/problems/0112.路径总和.md b/problems/0112.路径总和.md index 40df1e7a..51ee0872 100644 --- a/problems/0112.路径总和.md +++ b/problems/0112.路径总和.md @@ -312,6 +312,37 @@ Python： Go： +JavaScript： + +```javascript +/** + * @param {TreeNode} root + * @param {number} targetSum + * @return {boolean} + */ +let hasPathSum = function (root, targetSum) { + const traversal = (node, cnt) => { + // 遇到叶子节点，并且计数为0 + if (cnt === 0 && !node.left && !node.right) return true; + // 遇到叶子节点而没有找到合适的边(计数不为0)，直接返回 + if (!node.left && !node.right) return false; + + // 左（空节点不遍历）.遇到叶子节点返回true，则直接返回true + if (node.left && traversal(node.left, cnt - node.left.val)) return true; + // 右（空节点不遍历） + if (node.right && traversal(node.right, cnt - node.right.val)) return true; + return false; + }; + if (!root) return false; + return traversal(root, targetSum - root.val); + + // 精简代码: + // if (!root) return false; + // if (!root.left && !root.right && targetSum === root.val) return true; + // return hasPathSum(root.left, targetSum - root.val) || hasPathSum(root.right, targetSum - root.val); +}; +``` + From 07e99cf9ccb7f64d53ecca898fe4f233d9fbec00 Mon Sep 17 00:00:00 2001 From: HermanZzz Date: Wed, 12 May 2021 16:01:18 +0800 Subject: [PATCH 12/37] =?UTF-8?q?=E6=B7=BB=E5=8A=A00113.=E8=B7=AF=E5=BE=84?= =?UTF-8?q?=E6=80=BB=E5=92=8C-ii=20=E7=9A=84JavaScript=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 | 37 +++++++++++++++++++++++++++++++++++ 1 file changed, 37 insertions(+) diff --git a/problems/0112.路径总和.md b/problems/0112.路径总和.md index 51ee0872..718a2f5b 100644 --- a/problems/0112.路径总和.md +++ b/problems/0112.路径总和.md @@ -314,6 +314,8 @@ Go： JavaScript： +0112.路径总和 + ```javascript /** * @param {TreeNode} root @@ -321,6 +323,7 @@ JavaScript： * @return {boolean} */ let hasPathSum = function (root, targetSum) { + // 递归法 const traversal = (node, cnt) => { // 遇到叶子节点，并且计数为0 if (cnt === 0 && !node.left && !node.right) return true; @@ -343,6 +346,40 @@ let hasPathSum = function (root, targetSum) { }; ``` +0113.路径总和-ii + +```javascript +let pathSum = function (root, targetSum) { + // 递归法 + // 要遍历整个树找到所有路径，所以递归函数不需要返回值, 与112不同 + const res = []; + const travelsal = (node, cnt, path) => { + // 遇到了叶子节点且找到了和为sum的路径 + if (cnt === 0 && !node.left && !node.right) { + res.push([...path]); // 不能写res.push(path), 要深拷贝 + return; + } + if (!node.left && !node.right) return; // 遇到叶子节点而没有找到合适的边，直接返回 + // 左 （空节点不遍历） + if (node.left) { + path.push(node.left.val); + travelsal(node.left, cnt - node.left.val, path); // 递归 + path.pop(); // 回溯 + } + // 右 （空节点不遍历） + if (node.right) { + path.push(node.right.val); + travelsal(node.right, cnt - node.right.val, path); // 递归 + path.pop(); // 回溯 + } + return; + }; + if (!root) return res; + travelsal(root, targetSum - root.val, [root.val]); // 把根节点放进路径 + return res; +}; +``` + From f44cade011d2c3a20470b51156987c742f3e24b0 Mon Sep 17 00:00:00 2001 From: doo0301 Date: Wed, 12 May 2021 16:08:09 +0800 Subject: [PATCH 13/37] =?UTF-8?q?=E6=B7=BB=E5=8A=A0=200102.=E4=BA=8C?= =?UTF-8?q?=E5=8F=89=E6=A0=91=E7=9A=84=E5=B1=82=E5=BA=8F=E9=81=8D=E5=8E=86?= =?UTF-8?q?.md=20Java=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 | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) 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 8c34d415..be2e9dca 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 @@ -419,7 +419,8 @@ public: Java： -```Java +``` Java + class Solution { public List> resList=new ArrayList>(); From 346b0713d8821d2d7fd9000b6cb71086d8bc0f04 Mon Sep 17 00:00:00 2001 From: nanhuaibeian <49868746+nanhuaibeian@users.noreply.github.com> Date: Wed, 12 May 2021 16:48:22 +0800 Subject: [PATCH 14/37] =?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 添加1049.最后一块石头的重量 Java版本 --- .../1049.最后一块石头的重量II.md | 22 ++++++++++++++++++- 1 file changed, 21 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 6f654fac..2fdaaa6f 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 @@ -155,7 +155,27 @@ public: Java： - +```Java +class Solution { + public int lastStoneWeightII(int[] stones) { + int sum = 0; + for (int i : stones) { + sum += i; + } + int target = sum >> 1; + //初始化dp数组 + int[] dp = new int[target + 1]; + for (int i = 0; i < stones.length; i++) { + //采用倒叙 + for (int j = target; j >= stones[i]; j--) { + //两种情况，要么放，要么不放 + dp[j] = Math.max(dp[j], dp[j - stones[i]] + stones[i]); + } + } + return sum - 2 * dp[target]; + } +} +``` Python： From a1d15df5e0b334fbc9c2a326e878c88018e37bb7 Mon Sep 17 00:00:00 2001 From: nanhuaibeian <49868746+nanhuaibeian@users.noreply.github.com> Date: Wed, 12 May 2021 16:56:05 +0800 Subject: [PATCH 15/37] =?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 添加1049.最后一块石头的重量 Java版本 --- problems/1049.最后一块石头的重量II.md | 2 +- 1 file changed, 1 insertion(+), 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 2fdaaa6f..0ffd6a3e 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 @@ -166,7 +166,7 @@ class Solution { //初始化dp数组 int[] dp = new int[target + 1]; for (int i = 0; i < stones.length; i++) { - //采用倒叙 + //采用倒序 for (int j = target; j >= stones[i]; j--) { //两种情况，要么放，要么不放 dp[j] = Math.max(dp[j], dp[j - stones[i]] + stones[i]); From 6aaba6fdf96baac08a82f59788f1545cf812e792 Mon Sep 17 00:00:00 2001 From: simonhancrew <597494370@qq.com> Date: Wed, 12 May 2021 17:53:21 +0800 Subject: [PATCH 16/37] =?UTF-8?q?=E6=B7=BB=E5=8A=A00001.=E4=B8=A4=E6=95=B0?= =?UTF-8?q?=E4=B9=8B=E5=92=8C=20Python3=20Rust=20=E7=89=88=E6=9C=AC?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- problems/0001.两数之和.md | 34 ++++++++++++++++++++++++++++++++++ 1 file changed, 34 insertions(+) diff --git a/problems/0001.两数之和.md b/problems/0001.两数之和.md index 6c9d99dd..21f798a9 100644 --- a/problems/0001.两数之和.md +++ b/problems/0001.两数之和.md @@ -106,6 +106,18 @@ public int[] twoSum(int[] nums, int target) { Python： +```python3 +class Solution: + def twoSum(self, nums: List[int], target: int) -> List[int]: + hashmap={} + for ind,num in enumerate(nums): + hashmap[num] = ind + for i,num in enumerate(nums): + j = hashmap.get(target - num) + if j is not None and i!=j: + return [i,j] +``` + Go： @@ -122,6 +134,28 @@ func twoSum(nums []int, target int) []int { } ``` +Rust + +```rust +use std::collections::HashMap; + +impl Solution { + pub fn two_sum(nums: Vec, target: i32) -> Vec { + let mut map = HashMap::with_capacity(nums.len()); + + for i in 0..nums.len() { + if let Some(k) = map.get(&(target - nums[i])) { + if *k != i { + return vec![*k as i32, i as i32]; + } + } + map.insert(nums[i], i); + } + panic!("not found") + } +} +``` + From 45f970eb65e7934935871d03d5508e12130a8dfc Mon Sep 17 00:00:00 2001 From: nanhuaibeian <49868746+nanhuaibeian@users.noreply.github.com> Date: Wed, 12 May 2021 20:49:36 +0800 Subject: [PATCH 17/37] =?UTF-8?q?Update=200707.=E8=AE=BE=E8=AE=A1=E9=93=BE?= =?UTF-8?q?=E8=A1=A8.md?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- problems/0707.设计链表.md | 71 +++++++++++++++++++++++++++++++++++ 1 file changed, 71 insertions(+) diff --git a/problems/0707.设计链表.md b/problems/0707.设计链表.md index f98051c9..93133b55 100644 --- a/problems/0707.设计链表.md +++ b/problems/0707.设计链表.md @@ -157,7 +157,78 @@ private: Java： +```Java +class MyLinkedList { + //size存储链表元素的个数 + int size; + //虚拟头结点 + ListNode head; + //初始化链表 + public MyLinkedList() { + size = 0; + head = new ListNode(0); + } + + //获取第index个节点的数值 + public int get(int index) { + //如果index非法，返回-1 + if (index < 0 || index >= size) { + return -1; + } + ListNode currentNode = head; + //包含一个虚拟头节点，所以查找第 index+1 个节点 + for (int i = 0; i <= index; i++) { + currentNode = currentNode.next; + } + return currentNode.val; + } + + //在链表最前面插入一个节点 + public void addAtHead(int val) { + addAtIndex(0, val); + } + + //在链表的最后插入一个节点 + public void addAtTail(int val) { + addAtIndex(size, val); + } + + // 在第 index 个节点之前插入一个新节点，例如index为0，那么新插入的节点为链表的新头节点。 + // 如果 index 等于链表的长度，则说明是新插入的节点为链表的尾结点 + // 如果 index 大于链表的长度，则返回空 + public void addAtIndex(int index, int val) { + if (index > size) { + return; + } + if (index < 0) { + index = 0; + } + size++; + //找到要插入节点的前驱 + ListNode pred = head; + for (int i = 0; i < index; i++) { + pred = pred.next; + } + ListNode toAdd = new ListNode(val); + toAdd.next = pred.next; + pred.next = toAdd; + } + + //删除第index个节点 + public void deleteAtIndex(int index) { + if (index < 0 || index >= size) { + return; + } + size--; + ListNode pred = head; + for (int i = 0; i < index; i++) { + pred = pred.next; + } + pred.next = pred.next.next; + } +} +``` Python： From a522c18365d61deac3d8bb4e7dc72f036da6073e Mon Sep 17 00:00:00 2001 From: nanhuaibeian <49868746+nanhuaibeian@users.noreply.github.com> Date: Wed, 12 May 2021 20:51:36 +0800 Subject: [PATCH 18/37] =?UTF-8?q?Update=200746.=E4=BD=BF=E7=94=A8=E6=9C=80?= =?UTF-8?q?=E5=B0=8F=E8=8A=B1=E8=B4=B9=E7=88=AC=E6=A5=BC=E6=A2=AF.md?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- problems/0746.使用最小花费爬楼梯.md | 21 +++++++++++++++++++- 1 file changed, 20 insertions(+), 1 deletion(-) diff --git a/problems/0746.使用最小花费爬楼梯.md b/problems/0746.使用最小花费爬楼梯.md index e87f782c..b8158205 100644 --- a/problems/0746.使用最小花费爬楼梯.md +++ b/problems/0746.使用最小花费爬楼梯.md @@ -203,7 +203,26 @@ public: Java： - +```Java +class Solution { + public int minCostClimbingStairs(int[] cost) { + if (cost == null || cost.length == 0) { + return 0; + } + if (cost.length == 1) { + return cost[0]; + } + int[] dp = new int[cost.length]; + dp[0] = cost[0]; + dp[1] = cost[1]; + for (int i = 2; i < cost.length; i++) { + dp[i] = Math.min(dp[i - 1], dp[i - 2]) + cost[i]; + } + //最后一步，如果是由倒数第二步爬，则最后一步的体力花费可以不用算 + return Math.min(dp[cost.length - 1], dp[cost.length - 2]); + } +} +``` Python： From f07c41e9b96b38dd980e85e6687b147f47749963 Mon Sep 17 00:00:00 2001 From: nanhuaibeian <49868746+nanhuaibeian@users.noreply.github.com> Date: Wed, 12 May 2021 20:54:22 +0800 Subject: [PATCH 19/37] =?UTF-8?q?Update=200518.=E9=9B=B6=E9=92=B1=E5=85=91?= =?UTF-8?q?=E6=8D=A2II.md?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- problems/0518.零钱兑换II.md | 17 ++++++++++++++++- 1 file changed, 16 insertions(+), 1 deletion(-) diff --git a/problems/0518.零钱兑换II.md b/problems/0518.零钱兑换II.md index 46e52cc0..15c9d7d0 100644 --- a/problems/0518.零钱兑换II.md +++ b/problems/0518.零钱兑换II.md @@ -188,7 +188,22 @@ public: Java： - +```Java +class Solution { + public int change(int amount, int[] coins) { + //递推表达式 + int[] dp = new int[amount + 1]; + //初始化dp数组，表示金额为0时只有一种情况，也就是什么都不装 + dp[0] = 1; + for (int i = 0; i < coins.length; i++) { + for (int j = coins[i]; j <= amount; j++) { + dp[j] += dp[j - coins[i]]; + } + } + return dp[amount]; + } +} +``` Python： From 242c2120bbe15ce34187aba3aa5d35ed0a05914b Mon Sep 17 00:00:00 2001 From: nanhuaibeian <49868746+nanhuaibeian@users.noreply.github.com> Date: Wed, 12 May 2021 20:55:32 +0800 Subject: [PATCH 20/37] =?UTF-8?q?Update=200474.=E4=B8=80=E5=92=8C=E9=9B=B6?= =?UTF-8?q?.md?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- problems/0474.一和零.md | 28 +++++++++++++++++++++++++++- 1 file changed, 27 insertions(+), 1 deletion(-) diff --git a/problems/0474.一和零.md b/problems/0474.一和零.md index 7970c38e..4ec5fd4d 100644 --- a/problems/0474.一和零.md +++ b/problems/0474.一和零.md @@ -161,7 +161,33 @@ public: Java： - +```Java +class Solution { + public int findMaxForm(String[] strs, int m, int n) { + //dp[i][j]表示i个0和j个1时的最大子集 + int[][] dp = new int[m + 1][n + 1]; + int oneNum, zeroNum; + for (String str : strs) { + oneNum = 0; + zeroNum = 0; + for (char ch : str.toCharArray()) { + if (ch == '0') { + zeroNum++; + } else { + oneNum++; + } + } + //倒序遍历 + for (int i = m; i >= zeroNum; i--) { + for (int j = n; j >= oneNum; j--) { + dp[i][j] = Math.max(dp[i][j], dp[i - zeroNum][j - oneNum] + 1); + } + } + } + return dp[m][n]; + } +} +``` Python： From fab96e6c482e14c5b576aeef48fd1046d9bf45fc Mon Sep 17 00:00:00 2001 From: nanhuaibeian <49868746+nanhuaibeian@users.noreply.github.com> Date: Wed, 12 May 2021 20:56:06 +0800 Subject: [PATCH 21/37] =?UTF-8?q?Update=200454.=E5=9B=9B=E6=95=B0=E7=9B=B8?= =?UTF-8?q?=E5=8A=A0II.md?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- problems/0454.四数相加II.md | 31 ++++++++++++++++++++++++++++++- 1 file changed, 30 insertions(+), 1 deletion(-) diff --git a/problems/0454.四数相加II.md b/problems/0454.四数相加II.md index 71dcc1ae..a2ef928b 100644 --- a/problems/0454.四数相加II.md +++ b/problems/0454.四数相加II.md @@ -88,7 +88,36 @@ public: Java： - +```Java +class Solution { + public int fourSumCount(int[] nums1, int[] nums2, int[] nums3, int[] nums4) { + Map map = new HashMap<>(); + int temp; + int res = 0; + //统计两个数组中的元素之和，同时统计出现的次数，放入map + for (int i : nums1) { + for (int j : nums2) { + temp = i + j; + if (map.containsKey(temp)) { + map.put(temp, map.get(temp) + 1); + } else { + map.put(temp, 1); + } + } + } + //统计剩余的两个元素的和，在map中找是否存在相加为0的情况，同时记录次数 + for (int i : nums3) { + for (int j : nums4) { + temp = i + j; + if (map.containsKey(0 - temp)) { + res += map.get(0 - temp); + } + } + } + return res; + } +} +``` Python： From 156a82bbba2573b3e7325f14a3ef0740eeb2b692 Mon Sep 17 00:00:00 2001 From: nanhuaibeian <49868746+nanhuaibeian@users.noreply.github.com> Date: Wed, 12 May 2021 20:56:48 +0800 Subject: [PATCH 22/37] =?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 --- problems/0416.分割等和子集.md | 34 +++++++++++++++++++++++++++++ 1 file changed, 34 insertions(+) diff --git a/problems/0416.分割等和子集.md b/problems/0416.分割等和子集.md index 257c4d7d..789a7fb5 100644 --- a/problems/0416.分割等和子集.md +++ b/problems/0416.分割等和子集.md @@ -185,7 +185,41 @@ public: Java： +```Java +class Solution { + public boolean canPartition(int[] nums) { + int sum = 0; + for (int i : nums) { + sum += i; + } + if ((sum & 1) == 1) { + return false; + } + int length = nums.length; + int target = sum >> 1; + //dp[j]表示前i个元素可以找到相加等于j情况 + boolean[] dp = new boolean[target + 1]; + //对于第一个元素，只有当j=nums[0]时，才恰好填充满 + if (nums[0] <= target) { + dp[nums[0]] = true; + } + for (int i = 1; i < length; i++) { + //j由右往左直到nums[i] + for (int j = target; j >= nums[i]; j--) { + //只有两种情况，要么放，要么不放 + //取其中的TRUE值 + dp[j] = dp[j] || dp[j - nums[i]]; + } + //一旦满足，结束，因为只需要找到一组值即可 + if (dp[target]) { + return dp[target]; + } + } + return dp[target]; + } +} +``` Python： From fdb9785e443ac24c2a884bf844e5baac4b2dbb60 Mon Sep 17 00:00:00 2001 From: nanhuaibeian <49868746+nanhuaibeian@users.noreply.github.com> Date: Wed, 12 May 2021 20:57:14 +0800 Subject: [PATCH 23/37] =?UTF-8?q?Update=200383.=E8=B5=8E=E9=87=91=E4=BF=A1?= =?UTF-8?q?.md?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- problems/0383.赎金信.md | 24 ++++++++++++++++++++++++ 1 file changed, 24 insertions(+) diff --git a/problems/0383.赎金信.md b/problems/0383.赎金信.md index ca9b6061..742bfdc3 100644 --- a/problems/0383.赎金信.md +++ b/problems/0383.赎金信.md @@ -111,7 +111,31 @@ public: Java： +```Java +class Solution { + public boolean canConstruct(String ransomNote, String magazine) { + //记录杂志字符串出现的次数 + int[] arr = new int[26]; + int temp; + for (int i = 0; i < magazine.length(); i++) { + temp = magazine.charAt(i) - 'a'; + arr[temp]++; + } + for (int i = 0; i < ransomNote.length(); i++) { + temp = ransomNote.charAt(i) - 'a'; + //对于金信中的每一个字符都在数组中查找 + //找到相应位减一，否则找不到返回false + if (arr[temp] > 0) { + arr[temp]--; + } else { + return false; + } + } + return true; + } +} +``` Python： From 6c40ec595ad8fcf2e10a50279dbc331dc289d327 Mon Sep 17 00:00:00 2001 From: nanhuaibeian <49868746+nanhuaibeian@users.noreply.github.com> Date: Wed, 12 May 2021 20:57:43 +0800 Subject: [PATCH 24/37] =?UTF-8?q?Update=200377.=E7=BB=84=E5=90=88=E6=80=BB?= =?UTF-8?q?=E5=92=8C=E2=85=A3.md?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- problems/0377.组合总和Ⅳ.md | 16 ++++++++++++++++ 1 file changed, 16 insertions(+) diff --git a/problems/0377.组合总和Ⅳ.md b/problems/0377.组合总和Ⅳ.md index b0b83718..8f8cfd86 100644 --- a/problems/0377.组合总和Ⅳ.md +++ b/problems/0377.组合总和Ⅳ.md @@ -147,7 +147,23 @@ C++测试用例有超过两个树相加超过int的数据，所以需要在if里 Java： +```Java +class Solution { + public int combinationSum4(int[] nums, int target) { + int[] dp = new int[target + 1]; + dp[0] = 1; + for (int i = 0; i <= target; i++) { + for (int j = 0; j < nums.length; j++) { + if (i >= nums[j]) { + dp[i] += dp[i - nums[j]]; + } + } + } + return dp[target]; + } +} +``` Python： From d5c333f1bab065b663788cc2939cbd8484d7850b Mon Sep 17 00:00:00 2001 From: nanhuaibeian <49868746+nanhuaibeian@users.noreply.github.com> Date: Wed, 12 May 2021 20:58:17 +0800 Subject: [PATCH 25/37] =?UTF-8?q?Update=200322.=E9=9B=B6=E9=92=B1=E5=85=91?= =?UTF-8?q?=E6=8D=A2.md?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- problems/0322.零钱兑换.md | 26 +++++++++++++++++++++++++- 1 file changed, 25 insertions(+), 1 deletion(-) diff --git a/problems/0322.零钱兑换.md b/problems/0322.零钱兑换.md index fbb9c6df..e67695d8 100644 --- a/problems/0322.零钱兑换.md +++ b/problems/0322.零钱兑换.md @@ -181,7 +181,31 @@ public: Java： - +```Java +class Solution { + public int coinChange(int[] coins, int amount) { + int max = Integer.MAX_VALUE; + int[] dp = new int[amount + 1]; + //初始化dp数组为最大值 + for (int j = 0; j < dp.length; j++) { + dp[j] = max; + } + //当金额为0时需要的硬币数目为0 + dp[0] = 0; + for (int i = 0; i < coins.length; i++) { + //正序遍历：完全背包每个硬币可以选择多次 + for (int j = coins[i]; j <= amount; j++) { + //只有dp[j-coins[i]]不是初始最大值时，该位才有选择的必要 + if (dp[j - coins[i]] != max) { + //选择硬币数目最小的情况 + dp[j] = Math.min(dp[j], dp[j - coins[i]] + 1); + } + } + } + return dp[amount] == max ? -1 : dp[amount]; + } +} +``` Python： From b09bf150dab7b9161c956eeb94f17bd72eb759ad Mon Sep 17 00:00:00 2001 From: nanhuaibeian <49868746+nanhuaibeian@users.noreply.github.com> Date: Wed, 12 May 2021 20:58:47 +0800 Subject: [PATCH 26/37] =?UTF-8?q?Update=200055.=E8=B7=B3=E8=B7=83=E6=B8=B8?= =?UTF-8?q?=E6=88=8F.md?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- problems/0055.跳跃游戏.md | 20 +++++++++++++++++++- 1 file changed, 19 insertions(+), 1 deletion(-) diff --git a/problems/0055.跳跃游戏.md b/problems/0055.跳跃游戏.md index 0cad1fa7..179ac246 100644 --- a/problems/0055.跳跃游戏.md +++ b/problems/0055.跳跃游戏.md @@ -86,7 +86,25 @@ public: Java： - +```Java +class Solution { + public boolean canJump(int[] nums) { + if (nums.length == 1) { + return true; + } + //覆盖范围 + int coverRange = nums[0]; + //在覆盖范围内更新最大的覆盖范围 + for (int i = 0; i <= coverRange; i++) { + coverRange = Math.max(coverRange, i + nums[i]); + if (coverRange >= nums.length - 1) { + return true; + } + } + return false; + } +} +``` Python： From 2e15cc33308112a43356db56a26a5c2d54049f6b Mon Sep 17 00:00:00 2001 From: nanhuaibeian <49868746+nanhuaibeian@users.noreply.github.com> Date: Wed, 12 May 2021 20:59:19 +0800 Subject: [PATCH 27/37] =?UTF-8?q?Update=200045.=E8=B7=B3=E8=B7=83=E6=B8=B8?= =?UTF-8?q?=E6=88=8FII.md?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- problems/0045.跳跃游戏II.md | 31 ++++++++++++++++++++++++++++++- 1 file changed, 30 insertions(+), 1 deletion(-) diff --git a/problems/0045.跳跃游戏II.md b/problems/0045.跳跃游戏II.md index 2def83a9..b8e369e6 100644 --- a/problems/0045.跳跃游戏II.md +++ b/problems/0045.跳跃游戏II.md @@ -143,7 +143,36 @@ public: Java： - +```Java +class Solution { + public int jump(int[] nums) { + if (nums == null || nums.length == 0 || nums.length == 1) { + return 0; + } + //记录跳跃的次数 + int count=0; + //当前的覆盖最大区域 + int curDistance = 0; + //最大的覆盖区域 + int maxDistance = 0; + for (int i = 0; i < nums.length; i++) { + //在可覆盖区域内更新最大的覆盖区域 + maxDistance = Math.max(maxDistance,i+nums[i]); + //说明当前一步，再跳一步就到达了末尾 + if (maxDistance>=nums.length-1){ + count++; + break; + } + //走到当前覆盖的最大区域时，更新下一步可达的最大区域 + if (i==curDistance){ + curDistance = maxDistance; + count++; + } + } + return count; + } +} +``` Python： From f9505965999d971725136bd7e4f56cfc94cb5ab9 Mon Sep 17 00:00:00 2001 From: nanhuaibeian <49868746+nanhuaibeian@users.noreply.github.com> Date: Wed, 12 May 2021 20:59:49 +0800 Subject: [PATCH 28/37] =?UTF-8?q?Update=200040.=E7=BB=84=E5=90=88=E6=80=BB?= =?UTF-8?q?=E5=92=8CII.md?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- problems/0040.组合总和II.md | 36 +++++++++++++++++++++++++++++++++ 1 file changed, 36 insertions(+) diff --git a/problems/0040.组合总和II.md b/problems/0040.组合总和II.md index ffcbe212..50898016 100644 --- a/problems/0040.组合总和II.md +++ b/problems/0040.组合总和II.md @@ -255,7 +255,43 @@ public: Java： +```Java +class Solution { + List> lists = new ArrayList<>(); + Deque deque = new LinkedList<>(); + int sum = 0; + public List> combinationSum2(int[] candidates, int target) { + //为了将重复的数字都放到一起，所以先进行排序 + Arrays.sort(candidates); + //加标志数组，用来辅助判断同层节点是否已经遍历 + boolean[] flag = new boolean[candidates.length]; + backTracking(candidates, target, 0, flag); + return lists; + } + + public void backTracking(int[] arr, int target, int index, boolean[] flag) { + if (sum == target) { + lists.add(new ArrayList(deque)); + return; + } + for (int i = index; i < arr.length && arr[i] + sum <= target; i++) { + //出现重复节点，同层的第一个节点已经被访问过，所以直接跳过 + if (i > 0 && arr[i] == arr[i - 1] && !flag[i - 1]) { + continue; + } + flag[i] = true; + sum += arr[i]; + deque.push(arr[i]); + //每个节点仅能选择一次，所以从下一位开始 + backTracking(arr, target, i + 1, flag); + int temp = deque.pop(); + flag[i] = false; + sum -= temp; + } + } +} +``` Python： From 988211e8892fdba5c9c2b15a0489bd7734af946e Mon Sep 17 00:00:00 2001 From: nanhuaibeian <49868746+nanhuaibeian@users.noreply.github.com> Date: Wed, 12 May 2021 21:00:14 +0800 Subject: [PATCH 29/37] =?UTF-8?q?Update=200039.=E7=BB=84=E5=90=88=E6=80=BB?= =?UTF-8?q?=E5=92=8C.md?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- problems/0039.组合总和.md | 32 ++++++++++++++++++++++++++++++++ 1 file changed, 32 insertions(+) diff --git a/problems/0039.组合总和.md b/problems/0039.组合总和.md index f983a994..ab118ee0 100644 --- a/problems/0039.组合总和.md +++ b/problems/0039.组合总和.md @@ -236,7 +236,39 @@ public: Java： +```Java +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 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) { + 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(); + } + } +} +``` Python： From ea2c08f0cbf58f997f7e236039126e9869f95e6a Mon Sep 17 00:00:00 2001 From: weikunkun Date: Wed, 12 May 2021 21:07:20 +0800 Subject: [PATCH 30/37] =?UTF-8?q?=E6=B7=BB=E5=8A=A00203.=E7=A7=BB=E9=99=A4?= =?UTF-8?q?=E9=93=BE=E8=A1=A8=E5=85=83=E7=B4=A0=20Java=E7=89=88=E6=9C=AC?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- problems/0203.移除链表元素.md | 58 ++++++++++++++++++++++++++++- 1 file changed, 57 insertions(+), 1 deletion(-) diff --git a/problems/0203.移除链表元素.md b/problems/0203.移除链表元素.md index e6667091..9fca1ee0 100644 --- a/problems/0203.移除链表元素.md +++ b/problems/0203.移除链表元素.md @@ -138,7 +138,63 @@ public: Java： - +```java +/** + * 添加虚节点方式 + * 时间复杂度 O(n) + * 空间复杂度 O(1) + * @param head + * @param val + * @return + */ +public ListNode removeElements(ListNode head, int val) { + if (head == null) { + return head; + } + // 因为删除可能涉及到头节点，所以设置dummy节点，统一操作 + ListNode dummy = new ListNode(-1, head); + ListNode pre = dummy; + ListNode cur = head; + while (cur != null) { + if (cur.val == val) { + pre.next = cur.next; + } else { + pre = cur; + } + cur = cur.next; + } + return dummy.next; +} +/** + * 不添加虚拟节点方式 + * 时间复杂度 O(n) + * 空间复杂度 O(1) + * @param head + * @param val + * @return + */ +public ListNode removeElements(ListNode head, int val) { + while (head != null && head.val == val) { + head = head.next; + } + // 已经为null，提前退出 + if (head == null) { + return head; + } + // 已确定当前head.val != val + ListNode pre = head; + ListNode cur = head.next; + while (cur != null) { + if (cur.val == val) { + pre.next = cur.next; + } else { + pre = cur; + } + cur = cur.next; + } + return head; +} +``` Python： From 9fbdb32bcfe8f921d872ad4826076f2bd2bd8ad6 Mon Sep 17 00:00:00 2001 From: youngyangyang04 <826123027@qq.com> Date: Wed, 12 May 2021 21:14:26 +0800 Subject: [PATCH 31/37] =?UTF-8?q?=E6=9B=B4=E6=96=B0=E9=93=BE=E8=A1=A8?= =?UTF-8?q?=E4=B8=93=E9=A2=98?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- README.md | 9 +- .../0024.两两交换链表中的节点.md | 100 ++++++++++++++++++ 2 files changed, 105 insertions(+), 4 deletions(-) create mode 100644 problems/0024.两两交换链表中的节点.md diff --git a/README.md b/README.md index df397457..276c8313 100644 --- a/README.md +++ b/README.md @@ -116,10 +116,11 @@ 1. [关于链表，你该了解这些！](./problems/链表理论基础.md) 2. [链表：听说用虚拟头节点会方便很多？](./problems/0203.移除链表元素.md) 3. [链表：一道题目考察了常见的五个操作！](./problems/0707.设计链表.md) -4. [链表：听说过两天反转链表又写不出来了？](./problems/0206.翻转链表.md) -5. [链表：删除链表的倒数第 N 个结点](./problems/0019.删除链表的倒数第N个节点.md) -5. [链表：环找到了，那入口呢？](./problems/0142.环形链表II.md) -6. [链表：总结篇！](./problems/链表总结篇.md) +4. [链表：听说过两天反转链表又写不出来了？](./problems/0206.翻转链表.md) +5. [链表：两两交换链表中的节点](./problems/0024.两两交换链表中的节点.md) +6. [链表：删除链表的倒数第 N 个结点](./problems/0019.删除链表的倒数第N个节点.md) +7. [链表：环找到了，那入口呢？](./problems/0142.环形链表II.md) +8. [链表：总结篇！](./problems/链表总结篇.md) ## 哈希表 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 new file mode 100644 index 00000000..aa284279 --- /dev/null +++ b/problems/0024.两两交换链表中的节点.md @@ -0,0 +1,100 @@ + +

+ + + + +

+

欢迎大家参与本项目，贡献其他语言版本的代码，拥抱开源，让更多学习算法的小伙伴们收益！

+ +## 24. 两两交换链表中的节点 + +给定一个链表，两两交换其中相邻的节点，并返回交换后的链表。 + +你不能只是单纯的改变节点内部的值，而是需要实际的进行节点交换。 + + +![24.两两交换链表中的节点-题意](https://code-thinking.cdn.bcebos.com/pics/24.%E4%B8%A4%E4%B8%A4%E4%BA%A4%E6%8D%A2%E9%93%BE%E8%A1%A8%E4%B8%AD%E7%9A%84%E8%8A%82%E7%82%B9-%E9%A2%98%E6%84%8F.jpg) + +## 思路 + +这道题目正常模拟就可以了。 + +建议使用虚拟头结点，这样会方便很多，要不然每次针对头结点（没有前一个指针指向头结点），还要单独处理。 + +对虚拟头结点的操作，还不熟悉的话，可以看这篇[链表：听说用虚拟头节点会方便很多？](https://mp.weixin.qq.com/s/L5aanfALdLEwVWGvyXPDqA)。 + +接下来就是交换相邻两个元素了，**此时一定要画图，不画图，操作多个指针很容易乱，而且要操作的先后顺序** + +初始时，cur指向虚拟头结点，然后进行如下三步： + +![24.两两交换链表中的节点1](https://code-thinking.cdn.bcebos.com/pics/24.%E4%B8%A4%E4%B8%A4%E4%BA%A4%E6%8D%A2%E9%93%BE%E8%A1%A8%E4%B8%AD%E7%9A%84%E8%8A%82%E7%82%B91.png) + +操作之后，链表如下： + +![24.两两交换链表中的节点2](https://code-thinking.cdn.bcebos.com/pics/24.%E4%B8%A4%E4%B8%A4%E4%BA%A4%E6%8D%A2%E9%93%BE%E8%A1%A8%E4%B8%AD%E7%9A%84%E8%8A%82%E7%82%B92.png) + +看这个可能就更直观一些了： + + +![24.两两交换链表中的节点3](https://code-thinking.cdn.bcebos.com/pics/24.%E4%B8%A4%E4%B8%A4%E4%BA%A4%E6%8D%A2%E9%93%BE%E8%A1%A8%E4%B8%AD%E7%9A%84%E8%8A%82%E7%82%B93.png) + +对应的C++代码实现如下： （注释中详细和如上图中的三步做对应） + +```C++ +class Solution { +public: + ListNode* swapPairs(ListNode* head) { + ListNode* dummyHead = new ListNode(0); // 设置一个虚拟头结点 + dummyHead->next = head; // 将虚拟头结点指向head，这样方面后面做删除操作 + ListNode* cur = dummyHead; + while(cur->next != nullptr && cur->next->next != nullptr) { + ListNode* tmp = cur->next; // 记录临时节点 + ListNode* 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 dummyHead->next; + } +}; +``` +* 时间复杂度：$O(n)$ +* 空间复杂度：$O(1)$ + +## 拓展 + +**这里还是说一下，大家不必太在意力扣上执行用时，打败多少多少用户，这个统计不准确的。** + +做题的时候自己能分析出来时间复杂度就可以了，至于力扣上执行用时，大概看一下就行。 + +上面的代码我第一次提交执行用时8ms，打败6.5%的用户，差点吓到我了。 + +心想应该没有更好的方法了吧，也就O(n)的时间复杂度，重复提交几次，这样了： + +![24.两两交换链表中的节点](https://code-thinking.cdn.bcebos.com/pics/24.%E4%B8%A4%E4%B8%A4%E4%BA%A4%E6%8D%A2%E9%93%BE%E8%A1%A8%E4%B8%AD%E7%9A%84%E8%8A%82%E7%82%B9.png) + +力扣上的统计如果两份代码是 100ms 和 300ms的耗时，其实是需要注意的。 + +如果一个是 4ms 一个是 12ms，看上去好像是一个打败了80%，一个打败了20%，其实是没有差别的。 只不过是力扣上统计的误差而已。 + + +## 其他语言版本 + + +Java： + + +Python： + +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) +
From 2f2e25de61fb1eaef44485239d40129bab753c91 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?=E4=B8=80=E6=96=87?= <30338551+YiwenXie@users.noreply.github.com> Date: Wed, 12 May 2021 22:25:52 +0900 Subject: [PATCH 32/37] =?UTF-8?q?Update=200046.=E5=85=A8=E6=8E=92=E5=88=97?= =?UTF-8?q?.md?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 更新Java版本 --- problems/0046.全排列.md | 34 ++++++++++++++++++++++++++++++++++ 1 file changed, 34 insertions(+) diff --git a/problems/0046.全排列.md b/problems/0046.全排列.md index 5f7b1ac0..05d86785 100644 --- a/problems/0046.全排列.md +++ b/problems/0046.全排列.md @@ -147,7 +147,41 @@ public: Java： +```java +class Solution { + List> result = new ArrayList<>();// 存放符合条件结果的集合 + LinkedList path = new LinkedList<>();// 用来存放符合条件结果 + boolean[] used; + public List> permute(int[] nums) { + if (nums.length == 0){ + return result; + } + used = new boolean[nums.length]; + permuteHelper(nums); + return result; + } + private void permuteHelper(int[] nums){ + if (path.size() == nums.length){ + result.add(new ArrayList<>(path)); + return; + } + for (int i = 0; i < nums.length; i++){ + // if (path.contains(nums[i])){ + // continue; + // } + if (used[i]){ + continue; + } + used[i] = true; + path.add(nums[i]); + permuteHelper(nums); + path.removeLast(); + used[i] = false; + } + } +} +``` Python： From 7fa6fa8823397bee24d3d66a0cb59719404a6efc Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?=E4=B8=80=E6=96=87?= <30338551+YiwenXie@users.noreply.github.com> Date: Wed, 12 May 2021 22:32:06 +0900 Subject: [PATCH 33/37] =?UTF-8?q?=E6=B7=BB=E5=8A=A0=200037.=E8=A7=A3?= =?UTF-8?q?=E6=95=B0=E7=8B=AC.md=20Java=20=E7=89=88=E6=9C=AC?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- problems/0037.解数独.md | 65 ++++++++++++++++++++++++++++++++++++++ 1 file changed, 65 insertions(+) diff --git a/problems/0037.解数独.md b/problems/0037.解数独.md index 75e2d3cd..7b59fad9 100644 --- a/problems/0037.解数独.md +++ b/problems/0037.解数独.md @@ -219,7 +219,72 @@ public: Java： +```java +class Solution { + public void solveSudoku(char[][] board) { + solveSudokuHelper(board); + } + private boolean solveSudokuHelper(char[][] board){ + //「一个for循环遍历棋盘的行，一个for循环遍历棋盘的列， + // 一行一列确定下来之后，递归遍历这个位置放9个数字的可能性！」 + for (int i = 0; i < 9; i++){ // 遍历行 + for (int j = 0; j < 9; j++){ // 遍历列 + if (board[i][j] != '.'){ // 跳过原始数字 + continue; + } + for (char k = '1'; k <= '9'; k++){ // (i, j) 这个位置放k是否合适 + if (isValidSudoku(i, j, k, board)){ + board[i][j] = k; + if (solveSudokuHelper(board)){ // 如果找到合适一组立刻返回 + return true; + } + board[i][j] = '.'; + } + } + // 9个数都试完了，都不行，那么就返回false + return false; + // 因为如果一行一列确定下来了，这里尝试了9个数都不行，说明这个棋盘找不到解决数独问题的解！ + // 那么会直接返回， 「这也就是为什么没有终止条件也不会永远填不满棋盘而无限递归下去！」 + } + } + // 遍历完没有返回false，说明找到了合适棋盘位置了 + return true; + } + + /** + * 判断棋盘是否合法有如下三个维度: + * 同行是否重复 + * 同列是否重复 + * 9宫格里是否重复 + */ + private boolean isValidSudoku(int row, int col, char val, char[][] board){ + // 同行是否重复 + for (int i = 0; i < 9; i++){ + if (board[row][i] == val){ + return false; + } + } + // 同列是否重复 + for (int j = 0; j < 9; j++){ + if (board[j][col] == val){ + return false; + } + } + // 9宫格里是否重复 + int startRow = (row / 3) * 3; + int startCol = (col / 3) * 3; + for (int i = startRow; i < startRow + 3; i++){ + for (int j = startCol; j < startCol + 3; j++){ + if (board[i][j] == val){ + return false; + } + } + } + return true; + } +} +``` Python： From a77901400534ad01cddfca27ba6d2aa1e3cc791a Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?=E4=B8=80=E6=96=87?= <30338551+YiwenXie@users.noreply.github.com> Date: Wed, 12 May 2021 22:34:43 +0900 Subject: [PATCH 34/37] =?UTF-8?q?=E6=B7=BB=E5=8A=A0=200053.=E6=9C=80?= =?UTF-8?q?=E5=A4=A7=E5=AD=90=E5=BA=8F=E5=92=8C.md=20Java=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/0053.最大子序和.md | 20 +++++++++++++++++++- 1 file changed, 19 insertions(+), 1 deletion(-) diff --git a/problems/0053.最大子序和.md b/problems/0053.最大子序和.md index b8a9d748..b8b11a57 100644 --- a/problems/0053.最大子序和.md +++ b/problems/0053.最大子序和.md @@ -139,7 +139,25 @@ public: Java： - +```java +class Solution { + public int maxSubArray(int[] nums) { + if (nums.length == 1){ + return nums[0]; + } + int sum = Integer.MIN_VALUE; + int count = 0; + for (int i = 0; i < nums.length; i++){ + count += nums[i]; + sum = Math.max(sum, count); // 取区间累计的最大值（相当于不断确定最大子序终止位置） + if (count <= 0){ + count = 0; // 相当于重置最大子序起始位置，因为遇到负数一定是拉低总和 + } + } + return sum; + } +} +``` Python： From d9d1f669ba9a7eb7a8c17c9136a000e9673c7f5a Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?=E4=B8=80=E6=96=87?= <30338551+YiwenXie@users.noreply.github.com> Date: Wed, 12 May 2021 22:37:31 +0900 Subject: [PATCH 35/37] =?UTF-8?q?=E6=B7=BB=E5=8A=A0=200077.=E7=BB=84?= =?UTF-8?q?=E5=90=88.md=20Java=E7=89=88=E6=9C=AC?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- problems/0077.组合.md | 27 +++++++++++++++++++++++++++ 1 file changed, 27 insertions(+) diff --git a/problems/0077.组合.md b/problems/0077.组合.md index 3dfb5216..f31766e0 100644 --- a/problems/0077.组合.md +++ b/problems/0077.组合.md @@ -340,6 +340,33 @@ public: Java： +```java +class Solution { + List> result = new ArrayList<>(); + LinkedList path = new LinkedList<>(); + public List> combine(int n, int k) { + combineHelper(n, k, 1); + return result; + } + + /** + * 每次从集合中选取元素，可选择的范围随着选择的进行而收缩，调整可选择的范围，就是要靠startIndex + * @param startIndex 用来记录本层递归的中，集合从哪里开始遍历（集合就是[1,...,n] ）。 + */ + private void combineHelper(int n, int k, int startIndex){ + //终止条件 + if (path.size() == k){ + result.add(new ArrayList<>(path)); + return; + } + for (int i = startIndex; i <= n - (k - path.size()) + 1; i++){ + path.add(i); + combineHelper(n, k, i + 1); + path.removeLast(); + } + } +} +``` Python： From 06d8ddee515cb3ce994a37ec416adde34979b236 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?=E4=B8=80=E6=96=87?= <30338551+YiwenXie@users.noreply.github.com> Date: Wed, 12 May 2021 22:42:29 +0900 Subject: [PATCH 36/37] =?UTF-8?q?=E6=B7=BB=E5=8A=A0=200078.=E5=AD=90?= =?UTF-8?q?=E9=9B=86.md=20Java=E7=89=88=E6=9C=AC?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- problems/0078.子集.md | 26 ++++++++++++++++++++++++++ 1 file changed, 26 insertions(+) diff --git a/problems/0078.子集.md b/problems/0078.子集.md index 8c68843d..77854133 100644 --- a/problems/0078.子集.md +++ b/problems/0078.子集.md @@ -177,7 +177,33 @@ public: Java： +```java +class Solution { + List> result = new ArrayList<>();// 存放符合条件结果的集合 + LinkedList path = new LinkedList<>();// 用来存放符合条件结果 + public List> subsets(int[] nums) { + if (nums.length == 0){ + result.add(new ArrayList<>()); + return result; + } + Arrays.sort(nums); + subsetsHelper(nums, 0); + return result; + } + private void subsetsHelper(int[] nums, int startIndex){ + result.add(new ArrayList<>(path));//「遍历这个树的时候，把所有节点都记录下来，就是要求的子集集合」。 + if (startIndex >= nums.length){ //终止条件可不加 + return; + } + for (int i = startIndex; i < nums.length; i++){ + path.add(nums[i]); + subsetsHelper(nums, i + 1); + path.removeLast(); + } + } +} +``` Python： From e8f8e7b8034d0cb27af5634b3bbe207e8d7ee6bf Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?=E4=B8=80=E6=96=87?= <30338551+YiwenXie@users.noreply.github.com> Date: Wed, 12 May 2021 22:44:41 +0900 Subject: [PATCH 37/37] =?UTF-8?q?=E6=B7=BB=E5=8A=A0=200090.=E5=AD=90?= =?UTF-8?q?=E9=9B=86II.md=20Java=E7=89=88=E6=9C=AC?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- problems/0090.子集II.md | 35 ++++++++++++++++++++++++++++++++++- 1 file changed, 34 insertions(+), 1 deletion(-) diff --git a/problems/0090.子集II.md b/problems/0090.子集II.md index cc5fd571..47db79f7 100644 --- a/problems/0090.子集II.md +++ b/problems/0090.子集II.md @@ -172,7 +172,40 @@ if (i > startIndex && nums[i] == nums[i - 1] ) { Java： - +```java +class Solution { + List> result = new ArrayList<>();// 存放符合条件结果的集合 + LinkedList path = new LinkedList<>();// 用来存放符合条件结果 + boolean[] used; + public List> subsetsWithDup(int[] nums) { + if (nums.length == 0){ + result.add(path); + return result; + } + Arrays.sort(nums); + used = new boolean[nums.length]; + subsetsWithDupHelper(nums, 0); + return result; + } + + private void subsetsWithDupHelper(int[] nums, int startIndex){ + result.add(new ArrayList<>(path)); + if (startIndex >= nums.length){ + return; + } + for (int i = startIndex; i < nums.length; i++){ + if (i > 0 && nums[i] == nums[i - 1] && !used[i - 1]){ + continue; + } + path.add(nums[i]); + used[i] = true; + subsetsWithDupHelper(nums, i + 1); + path.removeLast(); + used[i] = false; + } + } +} +``` Python：