From 195504c0e03c8509d4921ef1d90b15059cf48466 Mon Sep 17 00:00:00 2001 From: jojoo15 <75017412+jojoo15@users.noreply.github.com> Date: Tue, 18 May 2021 11:33:32 +0200 Subject: [PATCH 01/31] =?UTF-8?q?Update=200617.=E5=90=88=E5=B9=B6=E4=BA=8C?= =?UTF-8?q?=E5=8F=89=E6=A0=91.md?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit python version of code added --- problems/0617.合并二叉树.md | 20 ++++++++++++++++++-- 1 file changed, 18 insertions(+), 2 deletions(-) diff --git a/problems/0617.合并二叉树.md b/problems/0617.合并二叉树.md index 848454de..ce37a953 100644 --- a/problems/0617.合并二叉树.md +++ b/problems/0617.合并二叉树.md @@ -312,7 +312,23 @@ class Solution { ``` Python： - +```python +# Definition for a binary tree node. +# class TreeNode: +# def __init__(self, val=0, left=None, right=None): +# self.val = val +# self.left = left +# self.right = right +//递归法*前序遍历 +class Solution: + def mergeTrees(self, root1: TreeNode, root2: TreeNode) -> TreeNode: + if not root1: return root2 // 如果t1为空，合并之后就应该是t2 + if not root2: return root1 // 如果t2为空，合并之后就应该是t1 + root1.val = root1.val + root2.val //中 + root1.left = self.mergeTrees(root1.left , root2.left) //左 + root1.right = self.mergeTrees(root1.right , root2.right) //右 + return root1 //root1修改了结构和数值 +``` Go： @@ -323,4 +339,4 @@ 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) -
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From 6d91454f18e0c5bdcb13412a976346d27b2d42ed Mon Sep 17 00:00:00 2001 From: Powerstot <77142630+Powerstot@users.noreply.github.com> Date: Tue, 18 May 2021 17:44:03 +0800 Subject: [PATCH 02/31] =?UTF-8?q?=E4=BF=AE=E6=94=B90232.=E7=94=A8=E6=A0=88?= =?UTF-8?q?=E5=AE=9E=E7=8E=B0=E9=98=9F=E5=88=97=20Java=E7=89=88=E6=9C=AC?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 修改0232.用栈实现队列 Java版本 --- problems/0232.用栈实现队列.md | 97 ++++++++++++++++++++++++++++- 1 file changed, 96 insertions(+), 1 deletion(-) diff --git a/problems/0232.用栈实现队列.md b/problems/0232.用栈实现队列.md index abdc363d..3cf058d7 100644 --- a/problems/0232.用栈实现队列.md +++ b/problems/0232.用栈实现队列.md @@ -131,6 +131,101 @@ public: Java： +使用Stack(堆栈)同名方法: +```java +class MyQueue { + // java中的 Stack 有设计上的缺陷，官方推荐使用 Deque(双端队列) 代替 Stack + Deque stIn; + Deque stOut; + /** Initialize your data structure here. */ + public MyQueue() { + stIn = new ArrayDeque<>(); + stOut = new ArrayDeque<>(); + } + + /** Push element x to the back of queue. */ + public void push(int x) { + stIn.push(x); + } + + /** Removes the element from in front of queue and returns that element. */ + public int pop() { + // 只要 stOut 为空，那么就应该将 stIn 中所有的元素倒腾到 stOut 中 + if (stOut.isEmpty()) { + while (!stIn.isEmpty()) { + stOut.push(stIn.pop()); + } + } + // 再返回 stOut 中的元素 + return stOut.pop(); + } + + /** Get the front element. */ + public int peek() { + // 直接使用已有的pop函数 + int res = this.pop(); + // 因为pop函数弹出了元素res，所以再添加回去 + stOut.push(res); + return res; + } + + /** Returns whether the queue is empty. */ + public boolean empty() { + // 当 stIn 栈为空时，说明没有元素可以倒腾到 stOut 栈了 + // 并且 stOut 栈也为空时，说明没有以前从 stIn 中倒腾到的元素了 + return stIn.isEmpty() && stOut.isEmpty(); + } +} +``` + +个人习惯写法，使用Deque通用api： +```java +class MyQueue { + // java中的 Stack 有设计上的缺陷，官方推荐使用 Deque(双端队列) 代替 Stack + // Deque 中的 addFirst、removeFirst、peekFirst 等方法等效于 Stack(堆栈) 中的 push、pop、peek + Deque stIn; + Deque stOut; + /** Initialize your data structure here. */ + public MyQueue() { + stIn = new ArrayDeque<>(); + stOut = new ArrayDeque<>(); + } + + /** Push element x to the back of queue. */ + public void push(int x) { + stIn.addLast(x); + } + + /** Removes the element from in front of queue and returns that element. */ + public int pop() { + // 只要 stOut 为空，那么就应该将 stIn 中所有的元素倒腾到 stOut 中 + if (stOut.isEmpty()) { + while (!stIn.isEmpty()) { + stOut.addLast(stIn.pollLast()); + } + } + // 再返回 stOut 中的元素 + return stOut.pollLast(); + } + + /** Get the front element. */ + public int peek() { + // 直接使用已有的pop函数 + int res = this.pop(); + // 因为pop函数弹出了元素res，所以再添加回去 + stOut.addLast(res); + return res; + } + + /** Returns whether the queue is empty. */ + public boolean empty() { + // 当 stIn 栈为空时，说明没有元素可以倒腾到 stOut 栈了 + // 并且 stOut 栈也为空时，说明没有以前从 stIn 中倒腾到的元素了 + return stIn.isEmpty() && stOut.isEmpty(); + } +} +``` + ```java class MyQueue { @@ -198,4 +293,4 @@ 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) -
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From 3169bc2688d702a1b8b367a6cf94db1ef88bf345 Mon Sep 17 00:00:00 2001 From: Powerstot <77142630+Powerstot@users.noreply.github.com> Date: Tue, 18 May 2021 17:52:35 +0800 Subject: [PATCH 03/31] =?UTF-8?q?=E4=BF=AE=E6=94=B90225.=E7=94=A8=E9=98=9F?= =?UTF-8?q?=E5=88=97=E5=AE=9E=E7=8E=B0=E6=A0=88=20Java=E7=89=88=E6=9C=AC?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 修改0225.用队列实现栈 Java版本 --- problems/0225.用队列实现栈.md | 90 ++++++++++++++++++++++++++++- 1 file changed, 89 insertions(+), 1 deletion(-) diff --git a/problems/0225.用队列实现栈.md b/problems/0225.用队列实现栈.md index 4018364a..8dff2b86 100644 --- a/problems/0225.用队列实现栈.md +++ b/problems/0225.用队列实现栈.md @@ -156,6 +156,7 @@ public: Java： +使用两个 Queue 实现 ```java class MyStack { @@ -205,7 +206,94 @@ class MyStack { * boolean param_4 = obj.empty(); */ ``` +使用两个 Deque 实现 +```java +class MyStack { + // Deque 接口继承了 Queue 接口 + // 所以 Queue 中的 add、poll、peek等效于 Deque 中的 addLast、pollFirst、peekFirst + Deque que1; // 和栈中保持一样元素的队列 + Deque que2; // 辅助队列 + /** Initialize your data structure here. */ + public MyStack() { + que1 = new ArrayDeque<>(); + que2 = new ArrayDeque<>(); + } + + /** Push element x onto stack. */ + public void push(int x) { + que1.addLast(x); + } + + /** Removes the element on top of the stack and returns that element. */ + public int pop() { + int size = que1.size(); + size--; + // 将 que1 导入 que2 ，但留下最后一个值 + while (size-- > 0) { + que2.addLast(que1.peekFirst()); + que1.pollFirst(); + } + int res = que1.pollFirst(); + // 将 que2 对象的引用赋给了 que1 ，此时 que1，que2 指向同一个队列 + que1 = que2; + // 如果直接操作 que2，que1 也会受到影响，所以为 que2 分配一个新的空间 + que2 = new ArrayDeque<>(); + return res; + } + + /** Get the top element. */ + public int top() { + return que1.peekLast(); + } + + /** Returns whether the stack is empty. */ + public boolean empty() { + return que1.isEmpty(); + } +} +``` +优化，使用一个 Deque 实现 +```java +class MyStack { + // Deque 接口继承了 Queue 接口 + // 所以 Queue 中的 add、poll、peek等效于 Deque 中的 addLast、pollFirst、peekFirst + Deque que1; + /** Initialize your data structure here. */ + public MyStack() { + que1 = new ArrayDeque<>(); + } + + /** Push element x onto stack. */ + public void push(int x) { + que1.addLast(x); + } + + /** Removes the element on top of the stack and returns that element. */ + public int pop() { + int size = que1.size(); + size--; + // 将 que1 导入 que2 ，但留下最后一个值 + while (size-- > 0) { + que1.addLast(que1.peekFirst()); + que1.pollFirst(); + } + + int res = que1.pollFirst(); + return res; + } + + /** Get the top element. */ + public int top() { + return que1.peekLast(); + } + + /** Returns whether the stack is empty. */ + public boolean empty() { + return que1.isEmpty(); + } +} +``` Python： @@ -276,4 +364,4 @@ 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) -
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From 0b3945cfd1a9b972839678b717f0f08461daae34 Mon Sep 17 00:00:00 2001 From: jojoo15 <75017412+jojoo15@users.noreply.github.com> Date: Tue, 18 May 2021 12:18:00 +0200 Subject: [PATCH 04/31] =?UTF-8?q?Update=200700.=E4=BA=8C=E5=8F=89=E6=90=9C?= =?UTF-8?q?=E7=B4=A2=E6=A0=91=E4=B8=AD=E7=9A=84=E6=90=9C=E7=B4=A2.md?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit recursive python version of code modified --- problems/0700.二叉搜索树中的搜索.md | 17 +++++++++++------ 1 file changed, 11 insertions(+), 6 deletions(-) diff --git a/problems/0700.二叉搜索树中的搜索.md b/problems/0700.二叉搜索树中的搜索.md index 277ef681..3e35fbfb 100644 --- a/problems/0700.二叉搜索树中的搜索.md +++ b/problems/0700.二叉搜索树中的搜索.md @@ -212,13 +212,18 @@ Python： 递归法： ```python +# Definition for a binary tree node. +# class TreeNode: +# def __init__(self, val=0, left=None, right=None): +# self.val = val +# self.left = left +# self.right = right class Solution: def searchBST(self, root: TreeNode, val: int) -> TreeNode: - if root is None: - return None - if val < root.val: return self.searchBST(root.left, val) - elif val > root.val: return self.searchBST(root.right, val) - else: return root + if not root or root.val == val: return root //为空或者已经找到都是直接返回root，所以合并了 + if root.val > val: return self.searchBST(root.left,val) //注意一定要加return + else: return self.searchBST(root.right,val) + ``` 迭代法： @@ -243,4 +248,4 @@ 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) -
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From b857e4bcbd6b2cf2ae9df3224ec218000735eedc Mon Sep 17 00:00:00 2001 From: QuinnDK <39618652+QuinnDK@users.noreply.github.com> Date: Tue, 18 May 2021 21:19:49 +0800 Subject: [PATCH 05/31] =?UTF-8?q?Update=200232.=E7=94=A8=E6=A0=88=E5=AE=9E?= =?UTF-8?q?=E7=8E=B0=E9=98=9F=E5=88=97.md?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- problems/0232.用栈实现队列.md | 69 ++++++++++++++++++++++++++++- 1 file changed, 68 insertions(+), 1 deletion(-) diff --git a/problems/0232.用栈实现队列.md b/problems/0232.用栈实现队列.md index abdc363d..8bf646a4 100644 --- a/problems/0232.用栈实现队列.md +++ b/problems/0232.用栈实现队列.md @@ -190,6 +190,73 @@ Python： Go： +```Go +type MyQueue struct { + stack []int + back []int +} + +/** Initialize your data structure here. */ +func Constructor() MyQueue { + return MyQueue{ + stack: make([]int, 0), + back: make([]int, 0), + } +} + +/** Push element x to the back of queue. */ +func (this *MyQueue) Push(x int) { + for len(this.back) != 0 { + val := this.back[len(this.back)-1] + this.back = this.back[:len(this.back)-1] + this.stack = append(this.stack, val) + } + this.stack = append(this.stack, x) +} + +/** Removes the element from in front of queue and returns that element. */ +func (this *MyQueue) Pop() int { + for len(this.stack) != 0 { + val := this.stack[len(this.stack)-1] + this.stack = this.stack[:len(this.stack)-1] + this.back = append(this.back, val) + } + if len(this.back) == 0 { + return 0 + } + val := this.back[len(this.back)-1] + this.back = this.back[:len(this.back)-1] + return val +} + +/** Get the front element. */ +func (this *MyQueue) Peek() int { + for len(this.stack) != 0 { + val := this.stack[len(this.stack)-1] + this.stack = this.stack[:len(this.stack)-1] + this.back = append(this.back, val) + } + if len(this.back) == 0 { + return 0 + } + val := this.back[len(this.back)-1] + return val +} + +/** Returns whether the queue is empty. */ +func (this *MyQueue) Empty() bool { + return len(this.stack) == 0 && len(this.back) == 0 +} + +/** + * Your MyQueue object will be instantiated and called as such: + * obj := Constructor(); + * obj.Push(x); + * param_2 := obj.Pop(); + * param_3 := obj.Peek(); + * param_4 := obj.Empty(); + */ + ``` @@ -198,4 +265,4 @@ 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) -
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From dcd7962774eba5e0092c514a26e10d9a7d857719 Mon Sep 17 00:00:00 2001 From: QuinnDK <39618652+QuinnDK@users.noreply.github.com> Date: Tue, 18 May 2021 21:22:33 +0800 Subject: [PATCH 06/31] =?UTF-8?q?Update=200516.=E6=9C=80=E9=95=BF=E5=9B=9E?= =?UTF-8?q?=E6=96=87=E5=AD=90=E5=BA=8F=E5=88=97.md?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- problems/0516.最长回文子序列.md | 30 +++++++++++++++++++++++++- 1 file changed, 29 insertions(+), 1 deletion(-) diff --git a/problems/0516.最长回文子序列.md b/problems/0516.最长回文子序列.md index d7acef99..d2253a4e 100644 --- a/problems/0516.最长回文子序列.md +++ b/problems/0516.最长回文子序列.md @@ -173,7 +173,35 @@ Python： Go： - +```Go +func longestPalindromeSubseq(s string) int { + str:=[]byte(s) + dp:=make([][]int,len(s)) + for i:=0;i=0;j--{ + if str[i]==str[j]{ + if j==i-1{ + dp[j][i]=2 + }else{ + dp[j][i]=dp[j+1][i-1]+2 + } + }else{ + dp[j][i]=Max(dp[j+1][i],dp[j][i-1]) + } + } + } + return dp[0][len(s)-1] +} +func Max(a,b int)int{ + if a>b{ + return a + } + return b +} +``` From 53168265e88a903257da119c1522a081675b2fbd Mon Sep 17 00:00:00 2001 From: jojoo15 <75017412+jojoo15@users.noreply.github.com> Date: Tue, 18 May 2021 15:35:24 +0200 Subject: [PATCH 07/31] =?UTF-8?q?Update=200098.=E9=AA=8C=E8=AF=81=E4=BA=8C?= =?UTF-8?q?=E5=8F=89=E6=90=9C=E7=B4=A2=E6=A0=91.md?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit python version of code added --- problems/0098.验证二叉搜索树.md | 24 +++++++++++++++++++++--- 1 file changed, 21 insertions(+), 3 deletions(-) diff --git a/problems/0098.验证二叉搜索树.md b/problems/0098.验证二叉搜索树.md index d8945eff..a3f78c39 100644 --- a/problems/0098.验证二叉搜索树.md +++ b/problems/0098.验证二叉搜索树.md @@ -336,8 +336,26 @@ class Solution { ``` Python： - - +```python +# Definition for a binary tree node. +# class TreeNode: +# def __init__(self, val=0, left=None, right=None): +# self.val = val +# self.left = left +# self.right = right +//递归法 +class Solution: + def isValidBST(self, root: TreeNode) -> bool: + res = [] //把二叉搜索树按中序遍历写成list + def buildalist(root): + if not root: return + buildalist(root.left) //左 + res.append(root.val) //中 + buildalist(root.right) //右 + return res + buildalist(root) + return res == sorted(res) and len(set(res)) == len(res) //检查list里的数有没有重复元素，以及是否按从小到大排列 +``` Go： ```Go import "math" @@ -365,4 +383,4 @@ func isBST(root *TreeNode, min, max int) bool { * 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) -
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From 4f96f64e3d6f54eac978bdea355c22060f80d1ee Mon Sep 17 00:00:00 2001 From: jojoo15 <75017412+jojoo15@users.noreply.github.com> Date: Tue, 18 May 2021 15:59:48 +0200 Subject: [PATCH 08/31] =?UTF-8?q?Update=200530.=E4=BA=8C=E5=8F=89=E6=90=9C?= =?UTF-8?q?=E7=B4=A2=E6=A0=91=E7=9A=84=E6=9C=80=E5=B0=8F=E7=BB=9D=E5=AF=B9?= =?UTF-8?q?=E5=B7=AE.md?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit added python version of code --- .../0530.二叉搜索树的最小绝对差.md | 27 ++++++++++++++++--- 1 file changed, 24 insertions(+), 3 deletions(-) diff --git a/problems/0530.二叉搜索树的最小绝对差.md b/problems/0530.二叉搜索树的最小绝对差.md index 903ebf78..347d66d1 100644 --- a/problems/0530.二叉搜索树的最小绝对差.md +++ b/problems/0530.二叉搜索树的最小绝对差.md @@ -177,8 +177,29 @@ class Solution { ``` Python： - - +```python +# Definition for a binary tree node. +# class TreeNode: +# def __init__(self, val=0, left=None, right=None): +# self.val = val +# self.left = left +# self.right = right +class Solution: + def getMinimumDifference(self, root: TreeNode) -> int: + res = [] + r = float("inf") + def buildaList(root): //把二叉搜索树转换成有序数组 + if not root: return None + if root.left: buildaList(root.left) //左 + res.append(root.val) //中 + if root.right: buildaList(root.right) //右 + return res + + buildaList(root) + for i in range(len(res)-1): // 统计有序数组的最小差值 + r = min(abs(res[i]-res[i+1]),r) + return r +``` Go： @@ -188,4 +209,4 @@ 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) -
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From 41272638670e6da93171dfce8af63d5da42d4e36 Mon Sep 17 00:00:00 2001 From: "qingyi.liu" Date: Tue, 18 May 2021 22:51:51 +0800 Subject: [PATCH 09/31] =?UTF-8?q?=E6=B7=BB=E5=8A=A0111.=E4=BA=8C=E5=8F=89?= =?UTF-8?q?=E6=A0=91=E7=9A=84=E6=9C=80=E5=B0=8F=E6=B7=B1=E5=BA=A6=20JavaSc?= =?UTF-8?q?ript=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 | 47 +++++++++++++++++++++++ 1 file changed, 47 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 01b6c89c..5605e13d 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 @@ -302,6 +302,53 @@ class Solution: Go： +JavaScript: + +递归法： + +```javascript +/** + * @param {TreeNode} root + * @return {number} + */ +var minDepth1 = function(root) { + if(!root) return 0; + // 到叶子节点 返回 1 + if(!root.left && !root.right) return 1; + // 只有右节点时 递归右节点 + if(!root.left) return 1 + minDepth(root.right);、 + // 只有左节点时 递归左节点 + if(!root.right) return 1 + minDepth(root.left); + return Math.min(minDepth(root.left), minDepth(root.right)) + 1; +}; +``` + +迭代法： + +```javascript +/** +* @param {TreeNode} root +* @return {number} +*/ +var minDepth = function(root) { + if(!root) return 0; + const queue = [root]; + let dep = 0; + while(true) { + let size = queue.length; + dep++; + while(size--){ + const node = queue.shift(); + // 到第一个叶子节点 返回 当前深度 + if(!node.left && !node.right) return dep; + node.left && queue.push(node.left); + node.right && queue.push(node.right); + } + } +}; +``` + + ----------------------- From cf6ec4f65a8ee43a15c29f0a380cfac5f809a8dd Mon Sep 17 00:00:00 2001 From: X-shuffle <53906918+X-shuffle@users.noreply.github.com> Date: Tue, 18 May 2021 22:58:00 +0800 Subject: [PATCH 10/31] =?UTF-8?q?Update=20=E4=BA=8C=E5=8F=89=E6=A0=91?= =?UTF-8?q?=E7=9A=84=E8=BF=AD=E4=BB=A3=E9=81=8D=E5=8E=86.md?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 添加 二叉树的迭代遍历 GO版本 --- problems/二叉树的迭代遍历.md | 102 +++++++++++++++++++++++++++ 1 file changed, 102 insertions(+) diff --git a/problems/二叉树的迭代遍历.md b/problems/二叉树的迭代遍历.md index 2647616b..d228077b 100644 --- a/problems/二叉树的迭代遍历.md +++ b/problems/二叉树的迭代遍历.md @@ -163,7 +163,109 @@ Python： Go： +> 迭代法前序遍历 +```go +//迭代法前序遍历 +/** + type Element struct { + // 元素保管的值 + Value interface{} + // 内含隐藏或非导出字段 +} + +func (l *List) Back() *Element +前序遍历：中左右 +压栈顺序：右左中 + **/ +func preorderTraversal(root *TreeNode) []int { + if root == nil { + return nil + } + var stack = list.New() + stack.PushBack(root.Right) + stack.PushBack(root.Left) + res:=[]int{} + res=append(res,root.Val) + for stack.Len()>0 { + e:=stack.Back() + stack.Remove(e) + node := e.Value.(*TreeNode)//e是Element类型，其值为e.Value.由于Value为接口，所以要断言 + if node==nil{ + continue + } + res=append(res,node.Val) + stack.PushBack(node.Right) + stack.PushBack(node.Left) + } + return res +} +``` + +> 迭代法后序遍历 + +```go +//后续遍历：左右中 +//压栈顺序：中右左(按照前序遍历思路)，再反转结果数组 +func postorderTraversal(root *TreeNode) []int { + if root == nil { + return nil + } + var stack = list.New() + stack.PushBack(root.Left) + stack.PushBack(root.Right) + res:=[]int{} + res=append(res,root.Val) + for stack.Len()>0 { + e:=stack.Back() + stack.Remove(e) + node := e.Value.(*TreeNode)//e是Element类型，其值为e.Value.由于Value为接口，所以要断言 + if node==nil{ + continue + } + res=append(res,node.Val) + stack.PushBack(node.Left) + stack.PushBack(node.Right) + } + for i:=0;i 迭代法中序遍历 + +```go +//迭代法中序遍历 +func inorderTraversal(root *TreeNode) []int { + rootRes:=[]int{} + if root==nil{ + return nil + } + stack:=list.New() + node:=root + //先将所有左节点找到，加入栈中 + for node!=nil{ + stack.PushBack(node) + node=node.Left + } + //其次对栈中的每个节点先弹出加入到结果集中，再找到该节点的右节点的所有左节点加入栈中 + for stack.Len()>0{ + e:=stack.Back() + node:=e.Value.(*TreeNode) + stack.Remove(e) + //找到该节点的右节点，再搜索他的所有左节点加入栈中 + rootRes=append(rootRes,node.Val) + node=node.Right + for node!=nil{ + stack.PushBack(node) + node=node.Left + } + } + return rootRes +} +``` From 1fcb8402232e4db9fb1af3312232f7c2e3f26ee5 Mon Sep 17 00:00:00 2001 From: tw2665 <55668073+tw2665@users.noreply.github.com> Date: Tue, 18 May 2021 15:45:10 -0400 Subject: [PATCH 11/31] =?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, 31 insertions(+) diff --git a/problems/0454.四数相加II.md b/problems/0454.四数相加II.md index a2ef928b..ad928a3f 100644 --- a/problems/0454.四数相加II.md +++ b/problems/0454.四数相加II.md @@ -121,6 +121,37 @@ class Solution { Python： +``` +class Solution(object): + def fourSumCount(self, nums1, nums2, nums3, nums4): + """ + :type nums1: List[int] + :type nums2: List[int] + :type nums3: List[int] + :type nums4: List[int] + :rtype: int + """ + # use a dict to store the elements in nums1 and nums2 and their sum + hashmap = dict() + for n1 in nums1: + for n2 in nums2: + if n1 + n2 in hashmap: + hashmap[n1+n2] += 1 + else: + hashmap[n1+n2] = 1 + + # if the -(a+b) exists in nums3 and nums4, we shall add the count + count = 0 + for n3 in nums3: + for n4 in nums4: + key = - n3 - n4 + if key in hashmap: + count += hashmap[key] + return count + + +``` + Go： From 830381313abb85357f180f6315e0e1c28c63c01d Mon Sep 17 00:00:00 2001 From: tw2665 <55668073+tw2665@users.noreply.github.com> Date: Tue, 18 May 2021 15:53:09 -0400 Subject: [PATCH 12/31] =?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 | 29 ++++++++++++++++++++++++++++- 1 file changed, 28 insertions(+), 1 deletion(-) diff --git a/problems/0383.赎金信.md b/problems/0383.赎金信.md index 2f7ae4d8..527945fa 100644 --- a/problems/0383.赎金信.md +++ b/problems/0383.赎金信.md @@ -136,7 +136,34 @@ class Solution { ``` Python： - +``` +class Solution(object): + def canConstruct(self, ransomNote, magazine): + """ + :type ransomNote: str + :type magazine: str + :rtype: bool + """ + + # use a dict to store the number of letter occurance in ransomNote + hashmap = dict() + for s in ransomNote: + if s in hashmap: + hashmap[s] += 1 + else: + hashmap[s] = 1 + + # check if the letter we need can be found in magazine + for l in magazine: + if l in hashmap: + hashmap[l] -= 1 + + for key in hashmap: + if hashmap[key] > 0: + return False + + return True +``` Go： From 9edc7aa01df2f652a170435870747a0896b0d83e Mon Sep 17 00:00:00 2001 From: charon2121 <66763177+charon2121@users.noreply.github.com> Date: Wed, 19 May 2021 08:28:50 +0800 Subject: [PATCH 13/31] =?UTF-8?q?=E6=9B=B4=E6=96=B0=20144.=E4=BA=8C?= =?UTF-8?q?=E5=8F=89=E6=A0=91=E7=9A=84=E5=89=8D=E5=BA=8F=E9=81=8D=E5=8E=86?= =?UTF-8?q?=20python3=E7=89=88=E6=9C=AC?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 更新 145.二叉树的后序遍历 python3版本 更新 94.二叉树的中序遍历 python3版本 --- problems/二叉树的迭代遍历.md | 62 ++++++++++++++++++++++++++++ 1 file changed, 62 insertions(+) diff --git a/problems/二叉树的迭代遍历.md b/problems/二叉树的迭代遍历.md index 2647616b..be2456de 100644 --- a/problems/二叉树的迭代遍历.md +++ b/problems/二叉树的迭代遍历.md @@ -160,6 +160,68 @@ Java： Python： +```python3 +# 前序遍历-迭代-LC144_二叉树的前序遍历 +class Solution: + def preorderTraversal(self, root: TreeNode) -> List[int]: + # 根结点为空则返回空列表 + if not root: + return [] + stack = [root] + result = [] + while stack: + node = stack.pop() + # 中结点先处理 + result.append(node.val) + # 右孩子先入栈 + if node.right: + stack.append(node.right) + # 左孩子后入栈 + if node.left: + stack.append(node.left) + return result + +# 中序遍历-迭代-LC94_二叉树的中序遍历 +class Solution: + def inorderTraversal(self, root: TreeNode) -> List[int]: + if not root: + return [] + stack = [] # 不能提前将root结点加入stack中 + result = [] + cur = root + while cur or stack: + # 先迭代访问最底层的左子树结点 + if cur: + stack.append(cur) + cur = cur.left + # 到达最左结点后处理栈顶结点 + else: + cur = stack.pop() + result.append(cur.val) + # 取栈顶元素右结点 + cur = cur.right + return result + +# 后序遍历-迭代-LC145_二叉树的后序遍历 +class Solution: + def postorderTraversal(self, root: TreeNode) -> List[int]: + if not root: + return [] + stack = [root] + result = [] + while stack: + node = stack.pop() + # 中结点先处理 + result.append(node.val) + # 左孩子先入栈 + if node.left: + stack.append(node.left) + # 右孩子后入栈 + if node.right: + stack.append(node.right) + # 将最终的数组翻转 + return result[::-1] +``` Go： From 44c8ce6a4f54869008961c62d2728548b6f24e04 Mon Sep 17 00:00:00 2001 From: X-shuffle <53906918+X-shuffle@users.noreply.github.com> Date: Wed, 19 May 2021 10:03:09 +0800 Subject: [PATCH 14/31] =?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=E8=BF=AD=E4=BB=A3=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 二叉树的迭代遍历 GO版本 --- problems/二叉树的迭代遍历.md | 1 - 1 file changed, 1 deletion(-) diff --git a/problems/二叉树的迭代遍历.md b/problems/二叉树的迭代遍历.md index d228077b..10e7e7b4 100644 --- a/problems/二叉树的迭代遍历.md +++ b/problems/二叉树的迭代遍历.md @@ -268,7 +268,6 @@ func inorderTraversal(root *TreeNode) []int { ``` - ----------------------- * 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 a57b6385c4ceccb7900cb9dc41a7eb3d6a59d2e5 Mon Sep 17 00:00:00 2001 From: X-shuffle <53906918+X-shuffle@users.noreply.github.com> Date: Wed, 19 May 2021 10:07:22 +0800 Subject: [PATCH 15/31] =?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=E8=BF=AD=E4=BB=A3=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 二叉树的迭代遍历 GO版本 --- problems/二叉树的迭代遍历.md | 1 + 1 file changed, 1 insertion(+) diff --git a/problems/二叉树的迭代遍历.md b/problems/二叉树的迭代遍历.md index 10e7e7b4..a1906469 100644 --- a/problems/二叉树的迭代遍历.md +++ b/problems/二叉树的迭代遍历.md @@ -205,6 +205,7 @@ func preorderTraversal(root *TreeNode) []int { > 迭代法后序遍历 ```go +//迭代法后序遍历 //后续遍历：左右中 //压栈顺序：中右左(按照前序遍历思路)，再反转结果数组 func postorderTraversal(root *TreeNode) []int { From c628620ceddbdbe236b1cbb6cc597431642ae260 Mon Sep 17 00:00:00 2001 From: QuinnDK <39618652+QuinnDK@users.noreply.github.com> Date: Wed, 19 May 2021 10:07:40 +0800 Subject: [PATCH 16/31] =?UTF-8?q?Update=200516.=E6=9C=80=E9=95=BF=E5=9B=9E?= =?UTF-8?q?=E6=96=87=E5=AD=90=E5=BA=8F=E5=88=97.md?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- problems/0516.最长回文子序列.md | 27 ++++++++++++++++++++++++++ 1 file changed, 27 insertions(+) diff --git a/problems/0516.最长回文子序列.md b/problems/0516.最长回文子序列.md index d7acef99..7736b69f 100644 --- a/problems/0516.最长回文子序列.md +++ b/problems/0516.最长回文子序列.md @@ -173,6 +173,33 @@ Python： Go： +```Go +func longestPalindromeSubseq(s string) int { + lenth:=len(s) + dp:=make([][]int,lenth) + for i:=0;i=0;i--{ + for j:=i+1;j Date: Wed, 19 May 2021 10:25:58 +0800 Subject: [PATCH 17/31] =?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 | 18 ++++++++++++++++++ 1 file changed, 18 insertions(+) diff --git a/problems/0055.跳跃游戏.md b/problems/0055.跳跃游戏.md index a25c831a..ae2cbd1e 100644 --- a/problems/0055.跳跃游戏.md +++ b/problems/0055.跳跃游戏.md @@ -122,6 +122,24 @@ class Solution: ``` Go： +```Go +func canJUmp(nums []int) bool { + if len(nums)<=1{ + return true + } + dp:=make([]bool,len(nums)) + dp[0]=true + for i:=1;i=0;j--{ + if dp[j]&&nums[j]+j>=i{ + dp[i]=true + break + } + } + } + return dp[len(nums)-1] +} +``` From 7a5008ef78993ce5b538148082f70dab3520947a Mon Sep 17 00:00:00 2001 From: QuinnDK <39618652+QuinnDK@users.noreply.github.com> Date: Wed, 19 May 2021 10:50:27 +0800 Subject: [PATCH 18/31] =?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 | 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 f65ceb9e..9b303a7c 100644 --- a/problems/0045.跳跃游戏II.md +++ b/problems/0045.跳跃游戏II.md @@ -193,6 +193,26 @@ class Solution: ``` Go： +```Go +func jump(nums []int) int { + dp:=make([]int ,len(nums)) + dp[0]=0 + + for i:=1;ii{ + dp[i]=min(dp[j]+1,dp[i]) + } + } + } + return dp[len(nums)-1] +} +/* +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 22bd2751f622aa3019045dbca0624384c411d164 Mon Sep 17 00:00:00 2001 From: HuJian <502361472@qq.com> Date: Wed, 19 May 2021 10:56:39 +0800 Subject: [PATCH 19/31] =?UTF-8?q?=E6=9B=B4=E6=96=B00704.=E4=BA=8C=E5=88=86?= =?UTF-8?q?=E6=9F=A5=E6=89=BE,java=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 | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/problems/0704.二分查找.md b/problems/0704.二分查找.md index c7207364..8b000e41 100644 --- a/problems/0704.二分查找.md +++ b/problems/0704.二分查找.md @@ -153,6 +153,10 @@ Java： ```java class Solution { public int search(int[] nums, int target) { + // 避免当 target 小于nums[0] nums[nums.length - 1]时多次循环运算 + if (target < nums[0] || target > nums[nums.length - 1]) { + return -1; + } int left = 0, right = nums.length - 1; while (left <= right) { int mid = left + ((right - left) >> 1); From 7253dc9bc7aaec1fb8235d41ea75aa5eae1f606f Mon Sep 17 00:00:00 2001 From: "qingyi.liu" Date: Wed, 19 May 2021 11:08:53 +0800 Subject: [PATCH 20/31] =?UTF-8?q?=E6=B7=BB=E5=8A=A019.=E5=88=A0=E9=99=A4?= =?UTF-8?q?=E9=93=BE=E8=A1=A8=E7=9A=84=E5=80=92=E6=95=B0=E7=AC=ACN?= =?UTF-8?q?=E4=B8=AA=E8=8A=82=E7=82=B9javascript=E7=89=88=E6=9C=AC?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- ...0019.删除链表的倒数第N个节点.md | 22 +++++++++++++++++++ 1 file changed, 22 insertions(+) diff --git a/problems/0019.删除链表的倒数第N个节点.md b/problems/0019.删除链表的倒数第N个节点.md index 3b89dabd..920c8110 100644 --- a/problems/0019.删除链表的倒数第N个节点.md +++ b/problems/0019.删除链表的倒数第N个节点.md @@ -135,6 +135,28 @@ func removeNthFromEnd(head *ListNode, n int) *ListNode { } ``` +JavaScript: + +```js +/** + * @param {ListNode} head + * @param {number} n + * @return {ListNode} + */ +var removeNthFromEnd = function(head, n) { + let ret = new ListNode(0, head), + slow = fast = ret; + while(n--) fast = fast.next; + if(!fast) return ret.next; + while (fast.next) { + fast = fast.next; + slow = slow.next + }; + slow.next = slow.next.next; + return ret.next; +}; +``` + ----------------------- * 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 0a7682998d60cf02caab772ba74955baf1ad806e Mon Sep 17 00:00:00 2001 From: "qingyi.liu" Date: Wed, 19 May 2021 11:22:07 +0800 Subject: [PATCH 21/31] =?UTF-8?q?=E6=B7=BB=E5=8A=A0142.=E7=8E=AF=E5=BD=A2?= =?UTF-8?q?=E9=93=BE=E8=A1=A8IIjavascript=E7=89=88=E6=9C=AC?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- problems/0142.环形链表II.md | 44 +++++++++++++++++++++++++++++++++ 1 file changed, 44 insertions(+) diff --git a/problems/0142.环形链表II.md b/problems/0142.环形链表II.md index b3a53c07..71f5cc4c 100644 --- a/problems/0142.环形链表II.md +++ b/problems/0142.环形链表II.md @@ -258,6 +258,50 @@ Go： } ``` +javaScript + +```js +// 两种循环实现方式 +/** + * @param {ListNode} head + * @return {ListNode} + */ +// 先判断是否是环形链表 +var detectCycle = function(head) { + if(!head || !head.next) return null; + let slow =head.next, fast = head.next.next; + while(fast && fast.next && fast!== slow) { + slow = slow.next; + fast = fast.next.next; + } + if(!fast || !fast.next ) return null; + slow = head; + while (fast !== slow) { + slow = slow.next; + fast = fast.next; + } + return slow; +}; + +var detectCycle = function(head) { + if(!head || !head.next) return null; + let slow =head.next, fast = head.next.next; + while(fast && fast.next) { + slow = slow.next; + fast = fast.next.next; + if(fast == slow) { + slow = head; + while (fast !== slow) { + slow = slow.next; + fast = fast.next; + } + return slow; + } + } + return null; +}; +``` + ----------------------- * 作者微信：[程序员Carl](https://mp.weixin.qq.com/s/b66DFkOp8OOxdZC_xLZxfw) From c175eaf471fd370b5d6a46767a9e0ffe726a9a4a Mon Sep 17 00:00:00 2001 From: NevS <1173325467@qq.com> Date: Wed, 19 May 2021 11:33:21 +0800 Subject: [PATCH 22/31] =?UTF-8?q?=E6=B7=BB=E5=8A=A0=20704.=20=E4=BA=8C?= =?UTF-8?q?=E5=88=86=E6=9F=A5=E6=89=BE=20go=20=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 | 43 ++++++++++++++++++++++++++++++++++- 1 file changed, 42 insertions(+), 1 deletion(-) diff --git a/problems/0704.二分查找.md b/problems/0704.二分查找.md index c7207364..96bb1fed 100644 --- a/problems/0704.二分查找.md +++ b/problems/0704.二分查找.md @@ -210,6 +210,47 @@ class Solution: Go： +（版本一）左闭右闭区间 + +```go +func search(nums []int, target int) int { + high := len(nums)-1 + low := 0 + for low <= high { + mid := low + (high-low)/2 + if nums[mid] == target { + return mid + } else if nums[mid] > target { + high = mid-1 + } else { + low = mid+1 + } + } + return -1 +} +``` + +（版本二）左闭右开区间 + +```go +func search(nums []int, target int) int { + high := len(nums) + low := 0 + for low < high { + mid := low + (high-low)/2 + if nums[mid] == target { + return mid + } else if nums[mid] > target { + high = mid + } else { + low = mid+1 + } + } + return -1 +} +``` + + @@ -217,4 +258,4 @@ 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 3f16de6462d9d80bf44ec8d0adc95988fccbd028 Mon Sep 17 00:00:00 2001 From: "qingyi.liu" Date: Wed, 19 May 2021 11:42:18 +0800 Subject: [PATCH 23/31] =?UTF-8?q?=E6=B7=BB=E5=8A=A0=E7=AC=AC202=E9=A2=98.?= =?UTF-8?q?=20=E5=BF=AB=E4=B9=90=E6=95=B0javascript=E7=89=88=E6=9C=AC?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- problems/0202.快乐数.md | 34 ++++++++++++++++++++++++++++++++++ 1 file changed, 34 insertions(+) diff --git a/problems/0202.快乐数.md b/problems/0202.快乐数.md index 8c0dd1e7..90228b8c 100644 --- a/problems/0202.快乐数.md +++ b/problems/0202.快乐数.md @@ -112,6 +112,40 @@ Python： Go： +javaScript: + +```js +function getN(n) { + if (n == 1 || n == 0) return n; + let res = 0; + while (n) { + res += (n % 10) * (n % 10); + n = parseInt(n / 10); + } + return res; +} + +var isHappy = function(n) { + const sumSet = new Set(); + while (n != 1 && !sumSet.has(n)) { + sumSet.add(n); + n = getN(n); + } + return n == 1; +}; + +// 使用环形链表的思想 说明出现闭环 退出循环 +var isHappy = function(n) { + if (getN(n) == 1) return true; + let a = getN(n), b = getN(getN(n)); + // 如果 a === b + while (b !== 1 && getN(b) !== 1 && a !== b) { + a = getN(a); + b = getN(getN(b)); + } + return b === 1 || getN(b) === 1 ; +}; +``` From 142c4bb83dbb97eaba1616afdca72292add9d0e0 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?=E4=B8=A5=E7=95=85?= Date: Wed, 19 May 2021 14:20:31 +0800 Subject: [PATCH 24/31] =?UTF-8?q?feat:=20=E6=96=B0=E5=A2=9E0077=E7=BB=84?= =?UTF-8?q?=E5=90=88python=E3=80=81JavaScript=E8=A7=A3=E6=B3=95?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- problems/0077.组合.md | 39 ++++++++++++++++++++++++++++++++++++++- 1 file changed, 38 insertions(+), 1 deletion(-) diff --git a/problems/0077.组合.md b/problems/0077.组合.md index 1f0d6eb1..d9d4b17f 100644 --- a/problems/0077.组合.md +++ b/problems/0077.组合.md @@ -370,8 +370,45 @@ class Solution { Python： +```python +class Solution: + result: List[List[int]] = [] + path: List[int] = [] + def combine(self, n: int, k: int) -> List[List[int]]: + self.result = [] + self.combineHelper(n, k, 1) + return self.result - + def combineHelper(self, n: int, k: int, startIndex: int): + if (l := len(self.path)) == k: + self.result.append(self.path.copy()) + return + for i in range(startIndex, n - (k - l) + 2): + self.path.append(i) + self.combineHelper(n, k, i + 1) + self.path.pop() +``` +javascript +```javascript +let result = [] +let path = [] +var combine = function(n, k) { + result = [] + combineHelper(n, k, 1) + return result +}; +const combineHelper = (n, k, startIndex) => { + if (path.length === k) { + result.push([...path]) + return + } + for (let i = startIndex; i <= n - (k - path.length) + 1; ++i) { + path.push(i) + combineHelper(n, k, i + 1) + path.pop() + } +} +``` Go： ```Go var res [][]int From 1b635d82100bda2d956bed9d6ebbc22163d12b88 Mon Sep 17 00:00:00 2001 From: QuinnDK <39618652+QuinnDK@users.noreply.github.com> Date: Wed, 19 May 2021 14:28:01 +0800 Subject: [PATCH 25/31] =?UTF-8?q?Update=200139.=E5=8D=95=E8=AF=8D=E6=8B=86?= =?UTF-8?q?=E5=88=86.md?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- problems/0139.单词拆分.md | 22 ++++++++++++++++++++-- 1 file changed, 20 insertions(+), 2 deletions(-) diff --git a/problems/0139.单词拆分.md b/problems/0139.单词拆分.md index c6d8e43b..46ed641e 100644 --- a/problems/0139.单词拆分.md +++ b/problems/0139.单词拆分.md @@ -254,7 +254,25 @@ Python： Go： - +```Go +func wordBreak(s string,wordDict []string) bool { + wordDictSet:=make(map[string]bool) + for _,w:=range wordDict{ + wordDictSet[w]=true + } + dp:=make([]bool,len(s)+1) + dp[0]=true + for i:=1;i<=len(s);i++{ + for j:=0;j \ No newline at end of file +
From b8bb7786a41a78bca103f686398fd2801e43bdbb Mon Sep 17 00:00:00 2001 From: hk27xing <244798299@qq.com> Date: Wed, 19 May 2021 16:23:04 +0800 Subject: [PATCH 26/31] =?UTF-8?q?=E6=B7=BB=E5=8A=A00459.=E9=87=8D=E5=A4=8D?= =?UTF-8?q?=E7=9A=84=E5=AD=90=E5=AD=97=E7=AC=A6=E4=B8=B2Java=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/0459.重复的子字符串.md | 31 +++++++++++++++++++++++++- 1 file changed, 30 insertions(+), 1 deletion(-) 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 5abc999a..3a5f3b17 100644 --- a/problems/0459.重复的子字符串.md +++ b/problems/0459.重复的子字符串.md @@ -149,9 +149,38 @@ public: ## 其他语言版本 - Java： +```java +class Solution { + public boolean repeatedSubstringPattern(String s) { + if (s.equals("")) return false; + + int len = s.length(); + // 原串加个空格(哨兵)，使下标从1开始，这样j从0开始，也不用初始化了 + s = " " + s; + char[] chars = s.toCharArray(); + int[] next = new int[len + 1]; + + // 构造 next 数组过程，j从0开始(空格)，i从2开始 + for (int i = 2, j = 0; i <= len; i++) { + // 匹配不成功，j回到前一位置 next 数组所对应的值 + while (j > 0 && chars[i] != chars[j + 1]) j = next[j]; + // 匹配成功，j往后移 + if (chars[i] == chars[j + 1]) j++; + // 更新 next 数组的值 + next[i] = j; + } + + // 最后判断是否是重复的子字符串，这里 next[len] 即代表next数组末尾的值 + if (next[len] > 0 && len % (len - next[len]) == 0) { + return true; + } + return false; + } +} +``` + Python： From 8c77bb2565658fb19c3d1159988ff6c50804876b Mon Sep 17 00:00:00 2001 From: "qingyi.liu" Date: Wed, 19 May 2021 18:45:14 +0800 Subject: [PATCH 27/31] =?UTF-8?q?=E6=B7=BB=E5=8A=A0=E4=BA=8C=E5=8F=89?= =?UTF-8?q?=E6=A0=91=E7=9A=84=E9=80=92=E5=BD=92=E9=81=8D=E5=8E=86javascrip?= =?UTF-8?q?t=E7=89=88=E6=9C=AC?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- problems/二叉树的递归遍历.md | 37 +++++++++++++++++++++++++++- 1 file changed, 36 insertions(+), 1 deletion(-) 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 937ef603..2d571294 100644 --- a/problems/二叉树的递归遍历.md +++ b/problems/二叉树的递归遍历.md @@ -226,7 +226,7 @@ func PreorderTraversal(root *TreeNode) (res []int) { var traversal func(node *TreeNode) traversal = func(node *TreeNode) { if node == nil { - return + return } res = append(res,node.Val) traversal(node.Left) @@ -272,6 +272,41 @@ func PostorderTraversal(root *TreeNode) (res []int) { } ``` +javaScript: + +```js + +前序遍历: + +var preorderTraversal = function(root, res = []) { + if (!root) return res; + res.push(root.val); + preorderTraversal(root.left, res) + preorderTraversal(root.right, res) + return res; +}; + +中序遍历: + +var inorderTraversal = function(root, res = []) { + if (!root) return res; + inorderTraversal(root.left, res); + res.push(root.val); + inorderTraversal(root.right, res); + return res; +}; + +后序遍历: + +var postorderTraversal = function(root, res = []) { + if (!root) return res; + postorderTraversal(root.left, res); + postorderTraversal(root.right, res); + res.push(root.val); + return res; +}; +``` + From a5759ce09b133815ecd5e41e6ffc4c7ec4ff04c1 Mon Sep 17 00:00:00 2001 From: nmydt <62681228+nmydt@users.noreply.github.com> Date: Wed, 19 May 2021 19:42:37 +0800 Subject: [PATCH 28/31] =?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 | 83 +++++++++++++++++++++++++ 1 file changed, 83 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 3ea4eeaf..bc91eca0 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 @@ -153,8 +153,91 @@ public: Java： + 迭代法前序遍历代码如下: + ```java + class Solution { + + public List preorderTraversal(TreeNode root) { + List result = new LinkedList<>(); + Stack st = new Stack<>(); + if (root != null) st.push(root); + while (!st.empty()) { + TreeNode node = st.peek(); + if (node != null) { + st.pop(); // 将该节点弹出，避免重复操作，下面再将右中左节点添加到栈中 + if (node.right!=null) st.push(node.right); // 添加右节点（空节点不入栈） + if (node.left!=null) st.push(node.left); // 添加左节点（空节点不入栈） + st.push(node); // 添加中节点 + st.push(null); // 中节点访问过，但是还没有处理，加入空节点做为标记。 + + } else { // 只有遇到空节点的时候，才将下一个节点放进结果集 + st.pop(); // 将空节点弹出 + node = st.peek(); // 重新取出栈中元素 + st.pop(); + result.add(node.val); // 加入到结果集 + } + } + return result; + } +} + ``` + 迭代法中序遍历代码如下: + ```java + class Solution { + public List inorderTraversal(TreeNode root) { + List result = new LinkedList<>(); + Stack st = new Stack<>(); + if (root != null) st.push(root); + while (!st.empty()) { + TreeNode node = st.peek(); + if (node != null) { + st.pop(); // 将该节点弹出，避免重复操作，下面再将右中左节点添加到栈中 + if (node.right!=null) st.push(node.right); // 添加右节点（空节点不入栈） + st.push(node); // 添加中节点 + st.push(null); // 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!=null) st.push(node.left); // 添加左节点（空节点不入栈） + } else { // 只有遇到空节点的时候，才将下一个节点放进结果集 + st.pop(); // 将空节点弹出 + node = st.peek(); // 重新取出栈中元素 + st.pop(); + result.add(node.val); // 加入到结果集 + } + } + return result; + } +} + ``` + 迭代法后序遍历代码如下: + ```java + class Solution { + + public List postorderTraversal(TreeNode root) { + List result = new LinkedList<>(); + Stack st = new Stack<>(); + if (root != null) st.push(root); + while (!st.empty()) { + TreeNode node = st.peek(); + if (node != null) { + st.pop(); // 将该节点弹出，避免重复操作，下面再将右中左节点添加到栈中 + st.push(node); // 添加中节点 + st.push(null); // 中节点访问过，但是还没有处理，加入空节点做为标记。 + if (node.right!=null) st.push(node.right); // 添加右节点（空节点不入栈） + if (node.left!=null) st.push(node.left); // 添加左节点（空节点不入栈） + + } else { // 只有遇到空节点的时候，才将下一个节点放进结果集 + st.pop(); // 将空节点弹出 + node = st.peek(); // 重新取出栈中元素 + st.pop(); + result.add(node.val); // 加入到结果集 + } + } + return result; + } +} + + ``` Python： From 1c267dc06458dfb1708484b0edb20e8f61f7f190 Mon Sep 17 00:00:00 2001 From: "qingyi.liu" Date: Wed, 19 May 2021 20:05:13 +0800 Subject: [PATCH 29/31] =?UTF-8?q?=E6=B7=BB=E5=8A=A0=E4=BA=8C=E5=8F=89?= =?UTF-8?q?=E6=A0=91=E7=9A=84=E8=BF=AD=E4=BB=A3=E9=81=8D=E5=8E=86javaScrip?= =?UTF-8?q?t=E7=89=88=E6=9C=AC?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- problems/二叉树的迭代遍历.md | 64 ++++++++++++++++++++++++++++ 1 file changed, 64 insertions(+) diff --git a/problems/二叉树的迭代遍历.md b/problems/二叉树的迭代遍历.md index 594d498f..60dd73a8 100644 --- a/problems/二叉树的迭代遍历.md +++ b/problems/二叉树的迭代遍历.md @@ -330,6 +330,70 @@ func inorderTraversal(root *TreeNode) []int { } ``` +javaScript + +```js + +前序遍历: + +// 入栈 右 -> 左 +// 出栈 中 -> 左 -> 右 +var preorderTraversal = function(root, res = []) { + if(!root) return res; + const stack = [root]; + let cur = null; + while(stack.length) { + cur = stack.pop(); + res.push(cur.val); + cur.right && stack.push(cur.right); + cur.left && stack.push(cur.left); + } + return res; +}; + +中序遍历: + +// 入栈 左 -> 右 +// 出栈 左 -> 中 -> 右 + +var inorderTraversal = function(root, res = []) { + const stack = []; + let cur = root; + while(stack.length || cur) { + if(cur) { + stack.push(cur); + // 左 + cur = cur.left; + } else { + // --> 弹出 中 + cur = stack.pop(); + res.push(cur.val); + // 右 + cur = cur.right; + } + }; + return res; +}; + +后序遍历: + +// 入栈 左 -> 右 +// 出栈 中 -> 右 -> 左 结果翻转 + +var postorderTraversal = function(root, res = []) { + if (!root) return res; + const stack = [root]; + let cur = null; + do { + cur = stack.pop(); + res.push(cur.val); + cur.left && stack.push(cur.left); + cur.right && stack.push(cur.right); + } while(stack.length); + return res.reverse(); +}; +``` + ----------------------- * 作者微信：[程序员Carl](https://mp.weixin.qq.com/s/b66DFkOp8OOxdZC_xLZxfw) From af6340c400999bb0dc2e26d09407ea18b5ef38fb Mon Sep 17 00:00:00 2001 From: nmydt <62681228+nmydt@users.noreply.github.com> Date: Wed, 19 May 2021 20:51:11 +0800 Subject: [PATCH 30/31] =?UTF-8?q?Update=20=E4=BA=8C=E5=8F=89=E6=A0=91?= =?UTF-8?q?=E4=B8=AD=E9=80=92=E5=BD=92=E5=B8=A6=E7=9D=80=E5=9B=9E=E6=BA=AF?= =?UTF-8?q?.md?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 添加 二叉树：以为使用了递归，其实还隐藏着回溯 Java代码 --- problems/二叉树中递归带着回溯.md | 78 ++++++++++++++++++++++ 1 file changed, 78 insertions(+) diff --git a/problems/二叉树中递归带着回溯.md b/problems/二叉树中递归带着回溯.md index bf15e39b..3f874332 100644 --- a/problems/二叉树中递归带着回溯.md +++ b/problems/二叉树中递归带着回溯.md @@ -175,7 +175,85 @@ if (cur->right) { Java： + 100. 相同的树:递归代码 + ```java + class Solution { + public boolean compare(TreeNode tree1, TreeNode tree2) { + + if(tree1==null && tree2==null)return true; + if(tree1==null || tree2==null)return false; + if(tree1.val!=tree2.val)return false; + // 此时就是：左右节点都不为空，且数值相同的情况 + // 此时才做递归，做下一层的判断 + boolean compareLeft = compare(tree1.left, tree2.left); // 左子树：左、 右子树：左 + boolean compareRight = compare(tree1.right, tree2.right); // 左子树：右、 右子树：右 + boolean isSame = compareLeft && compareRight; // 左子树：中、 右子树：中（逻辑处理） + return isSame; + } + boolean isSameTree(TreeNode p, TreeNode q) { + return compare(p, q); + } +} + ``` + 257. 二叉树的所有路径: 回溯代码 + ```java + class Solution { + public void traversal(TreeNode cur, List path, List result) { + path.add(cur.val); + // 这才到了叶子节点 + if (cur.left == null && cur.right == null) { + String sPath=""; + for (int i = 0; i < path.size() - 1; i++) { + sPath += ""+path.get(i); + sPath += "->"; + } + sPath += path.get(path.size() - 1); + result.add(sPath); + return; + } + if (cur.left!=null) { + traversal(cur.left, path, result); + path.remove(path.size()-1); // 回溯 + } + if (cur.right!=null) { + traversal(cur.right, path, result); + path.remove(path.size()-1); // 回溯 + } + } + + public List binaryTreePaths(TreeNode root) { + List result = new LinkedList<>(); + List path = new LinkedList<>(); + if (root == null) return result; + traversal(root, path, result); + return result; + } +} + + ``` + 如下为精简之后的递归代码：(257. 二叉树的所有路径) + ```java + class Solution { + public void traversal(TreeNode cur, String path, List result) { + path += cur.val; // 中 + if (cur.left == null && cur.right == null) { + result.add(path); + return; + } + if (cur.left!=null) traversal(cur.left, path + "->", result); // 左 回溯就隐藏在这里 + if (cur.right!=null) traversal(cur.right, path + "->", result); // 右 回溯就隐藏在这里 + } + + public List binaryTreePaths(TreeNode root) { + List result = new LinkedList<>(); + String path = ""; + if (root == null) return result; + traversal(root, path, result); + return result; + } +} + ``` Python： From 9b52a5070c4a2e6c38023302b2c541dc59a94098 Mon Sep 17 00:00:00 2001 From: nmydt <62681228+nmydt@users.noreply.github.com> Date: Wed, 19 May 2021 21:13:30 +0800 Subject: [PATCH 31/31] =?UTF-8?q?=E6=B7=BB=E5=8A=A0=201035.=E4=B8=8D?= =?UTF-8?q?=E7=9B=B8=E4=BA=A4=E7=9A=84=E7=BA=BF=20Java=E7=89=88=E6=9C=AC?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- problems/1035.不相交的线.md | 19 ++++++++++++++++++- 1 file changed, 18 insertions(+), 1 deletion(-) diff --git a/problems/1035.不相交的线.md b/problems/1035.不相交的线.md index 6f2b6646..660b1e27 100644 --- a/problems/1035.不相交的线.md +++ b/problems/1035.不相交的线.md @@ -73,7 +73,24 @@ public: Java： - + ```java + class Solution { + public int maxUncrossedLines(int[] A, int[] B) { + int [][] dp = new int[A.length+1][B.length+1]; + for(int i=1;i<=A.length;i++) { + for(int j=1;j<=B.length;j++) { + if (A[i-1]==B[j-1]) { + dp[i][j]=dp[i-1][j-1]+1; + } + else { + dp[i][j]=Math.max(dp[i-1][j], dp[i][j-1]); + } + } + } + return dp[A.length][B.length]; + } +} + ``` Python：