From 932d27754cb34420926a41176f6fedb860768b44 Mon Sep 17 00:00:00 2001 From: Kelvin Date: Sat, 31 Jul 2021 23:04:46 -0400 Subject: [PATCH 01/14] =?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 修改逻辑与题解相同. --- problems/0617.合并二叉树.md | 25 ++++++++++++++++++------- 1 file changed, 18 insertions(+), 7 deletions(-) diff --git a/problems/0617.合并二叉树.md b/problems/0617.合并二叉树.md index 19b58bd3..c5eb7594 100644 --- a/problems/0617.合并二叉树.md +++ b/problems/0617.合并二叉树.md @@ -312,6 +312,8 @@ class Solution { ``` Python： + +**递归法 - 前序遍历** ```python # Definition for a binary tree node. # class TreeNode: @@ -319,16 +321,25 @@ Python： # 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 + # 递归终止条件: + # 但凡有一个节点为空, 就立刻返回另外一个. 如果另外一个也为None就直接返回None. + if not root1: + return root2 + if not root2: + return root1 + # 上面的递归终止条件保证了代码执行到这里root1, root2都非空. + 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 # ⚠️ 注意: 本题我们重复使用了题目给出的节点而不是创建新节点. 节省时间, 空间. +``` + +**迭代法** +```python # 迭代法-覆盖原来的树 class Solution: def mergeTrees(self, root1: TreeNode, root2: TreeNode) -> TreeNode: From 84a12f32de997868efcfff08d25c6a161fcc5cff Mon Sep 17 00:00:00 2001 From: Kelvin Date: Sat, 31 Jul 2021 23:10:30 -0400 Subject: [PATCH 02/14] =?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 迭代法: 逻辑没有改, 只是改变顺序使之与c++代码逻辑一致. --- problems/0617.合并二叉树.md | 51 ++++++++++++++++++-------------- 1 file changed, 29 insertions(+), 22 deletions(-) diff --git a/problems/0617.合并二叉树.md b/problems/0617.合并二叉树.md index c5eb7594..09d844f3 100644 --- a/problems/0617.合并二叉树.md +++ b/problems/0617.合并二叉树.md @@ -340,31 +340,38 @@ class Solution: **迭代法** ```python -# 迭代法-覆盖原来的树 class Solution: def mergeTrees(self, root1: TreeNode, root2: TreeNode) -> TreeNode: - if not root1: return root2 - if not root2: return root1 - # 迭代,将树2覆盖到树1 - queue1 = [root1] - queue2 = [root2] - root = root1 - while queue1 and queue2: - root1 = queue1.pop(0) - root2 = queue2.pop(0) - root1.val += root2.val - if not root1.left: # 如果树1左儿子不存在，则覆盖后树1的左儿子为树2的左儿子 - root1.left = root2.left - elif root1.left and root2.left: - queue1.append(root1.left) - queue2.append(root2.left) + if not root1: + return root2 + if not root2: + return root1 - if not root1.right: # 同理，处理右儿子 - root1.right = root2.right - elif root1.right and root2.right: - queue1.append(root1.right) - queue2.append(root2.right) - return root + queue = deque() + queue.append(root1) + queue.append(root2) + + while queue: + node1 = queue.popleft() + node2 = queue.popleft() + # 更新queue + # 只有两个节点都有左节点时, 再往queue里面放. + if node1.left and node2.left: + queue.append(node1.left) + queue.append(node2.left) + # 只有两个节点都有右节点时, 再往queue里面放. + if node1.right and node2.right: + queue.append(node1.right) + queue.append(node2.right) + + # 更新当前节点. 同时改变当前节点的左右孩子. + node1.val += node2.val + if not node1.left and node2.left: + node1.left = node2.left + if not node1.right and node2.right: + node1.right = node2.right + + return root1 ``` Go： From a8109b40141202dd9782f5389f0816c8057999c5 Mon Sep 17 00:00:00 2001 From: Kelvin Date: Sun, 1 Aug 2021 10:15:22 -0400 Subject: [PATCH 03/14] =?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 更改代码符合PEP 8 规范. --- problems/0700.二叉搜索树中的搜索.md | 21 +++++++++++--------- 1 file changed, 12 insertions(+), 9 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 d6899ac5..e6eb0358 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 @@ -212,17 +212,20 @@ 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 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) + # 为什么要有返回值: + # 因为搜索到目标节点就要立即return， + # 这样才是找到节点就返回（搜索某一条边），如果不加return，就是遍历整棵树了。 + + if not root or root.val == val: + return root + + if root.val > val: + return self.searchBST(root.left, val) + + if root.val < val: + return self.searchBST(root.right, val) ``` From 2a94d6ca0f413d461537f112cfb8b99855b13cd5 Mon Sep 17 00:00:00 2001 From: Kelvin Date: Sun, 1 Aug 2021 10:17:03 -0400 Subject: [PATCH 04/14] =?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 --- problems/0700.二叉搜索树中的搜索.md | 6 ++++++ 1 file changed, 6 insertions(+) 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 e6eb0358..4b02f8af 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 @@ -212,6 +212,12 @@ 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: # 为什么要有返回值: From 3ef151383e3e6aec9b4c6ae14e9dcfa2138f0b8b Mon Sep 17 00:00:00 2001 From: fixme Date: Sun, 1 Aug 2021 23:06:26 +0800 Subject: [PATCH 05/14] =?UTF-8?q?=E3=80=90707=5F=E8=AE=BE=E8=AE=A1?= =?UTF-8?q?=E9=93=BE=E8=A1=A8=E3=80=91=E5=A2=9E=E5=8A=A0C=E5=AE=9E?= =?UTF-8?q?=E7=8E=B0?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- problems/0707.设计链表.md | 122 ++++++++++++++++++++++++++++++++++ 1 file changed, 122 insertions(+) diff --git a/problems/0707.设计链表.md b/problems/0707.设计链表.md index 8be28f88..349e2409 100644 --- a/problems/0707.设计链表.md +++ b/problems/0707.设计链表.md @@ -154,7 +154,129 @@ private: ## 其他语言版本 +C: +```C +typedef struct { + int val; + struct MyLinkedList* next; +}MyLinkedList; +/** Initialize your data structure here. */ + +MyLinkedList* myLinkedListCreate() { + //这个题必须用虚拟头指针,参数都是一级指针,头节点确定后没法改指向了!!! + MyLinkedList* head = (MyLinkedList *)malloc(sizeof (MyLinkedList)); + head->next = NULL; + return head; +} + +/** Get the value of the index-th node in the linked list. If the index is invalid, return -1. */ +int myLinkedListGet(MyLinkedList* obj, int index) { + MyLinkedList *cur = obj->next; + for (int i = 0; cur != NULL; i++){ + if (i == index){ + return cur->val; + } + else{ + cur = cur->next; + } + } + return -1; +} + +/** Add a node of value val before the first element of the linked list. After the insertion, the new node will be the first node of the linked list. */ +void myLinkedListAddAtHead(MyLinkedList* obj, int val) { + MyLinkedList *nhead = (MyLinkedList *)malloc(sizeof (MyLinkedList)); + nhead->val = val; + nhead->next = obj->next; + obj->next = nhead; + +} + +/** Append a node of value val to the last element of the linked list. */ +void myLinkedListAddAtTail(MyLinkedList* obj, int val) { + MyLinkedList *cur = obj; + while(cur->next != NULL){ + cur = cur->next; + } + MyLinkedList *ntail = (MyLinkedList *)malloc(sizeof (MyLinkedList)); + ntail->val = val; + ntail->next = NULL; + cur->next = ntail; +} + +/** Add a node of value val before the index-th node in the linked list. If index equals to the length of linked list, the node will be appended to the end of linked list. If index is greater than the length, the node will not be inserted. */ +void myLinkedListAddAtIndex(MyLinkedList* obj, int index, int val) { + if (index == 0){ + myLinkedListAddAtHead(obj, val); + return; + } + MyLinkedList *cur = obj->next; + for (int i = 1 ;cur != NULL; i++){ + if (i == index){ + MyLinkedList* newnode = (MyLinkedList *)malloc(sizeof (MyLinkedList)); + newnode->val = val; + newnode->next = cur->next; + cur->next = newnode; + return; + } + else{ + cur = cur->next; + } + } +} + +/** Delete the index-th node in the linked list, if the index is valid. */ +void myLinkedListDeleteAtIndex(MyLinkedList* obj, int index) { + if (index == 0){ + MyLinkedList *tmp = obj->next; + if (tmp != NULL){ + obj->next = tmp->next; + free(tmp) + } + return; + } + MyLinkedList *cur = obj->next; + for (int i = 1 ;cur != NULL && cur->next != NULL; i++){ + if (i == index){ + MyLinkedList *tmp = cur->next; + if (tmp != NULL) { + cur->next = tmp->next; + free(tmp); + } + return; + } + else{ + cur = cur->next; + } + } + +} + +void myLinkedListFree(MyLinkedList* obj) { + while(obj != NULL){ + MyLinkedList *tmp = obj; + obj = obj->next; + free(tmp); + } +} + +/** + * Your MyLinkedList struct will be instantiated and called as such: + * MyLinkedList* obj = myLinkedListCreate(); + * int param_1 = myLinkedListGet(obj, index); + + * myLinkedListAddAtHead(obj, val); + + * myLinkedListAddAtTail(obj, val); + + * myLinkedListAddAtIndex(obj, index, val); + + * myLinkedListDeleteAtIndex(obj, index); + + * myLinkedListFree(obj); +*/ +``` Java： ```Java From b87d619cdd1ab886055d94cb4b878f550fe51ea7 Mon Sep 17 00:00:00 2001 From: Kelvin Date: Sun, 1 Aug 2021 13:54:51 -0400 Subject: [PATCH 06/14] =?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 更改递归部分代码 1. 更新上一版代码格式 使其更符合PEP8. 2. 把代码细节都暴露出来, 逻辑更加清晰. --- problems/0098.验证二叉搜索树.md | 34 ++++++++++++++++++-------- 1 file changed, 24 insertions(+), 10 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 248d10f1..a271b977 100644 --- a/problems/0098.验证二叉搜索树.md +++ b/problems/0098.验证二叉搜索树.md @@ -337,6 +337,8 @@ class Solution { ``` Python： + +**递归** - 利用BST中序遍历特性 ```python # Definition for a binary tree node. # class TreeNode: @@ -344,18 +346,30 @@ Python： # 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 + # 思路: 利用BST中序遍历的特性. + # 中序遍历输出的二叉搜索树节点的数值是有序序列 + candidate_list = [] + + def __traverse(root: TreeNode) -> None: + nonlocal candidate_list + if not root: + return + __traverse(root.left) + candidate_list.append(root.val) + __traverse(root.right) + + def __is_sorted(nums: list) -> bool: + for i in range(1, len(nums)): + if nums[i] <= nums[i - 1]: + return False + return True + + __traverse(root) + res = __is_sorted(candidate_list) + + return res # 简单递归法 class Solution: From 6178dff832cebd336c596ae40ae941ab28cd42c2 Mon Sep 17 00:00:00 2001 From: Kelvin Date: Sun, 1 Aug 2021 13:57:12 -0400 Subject: [PATCH 07/14] =?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 增加comment --- problems/0098.验证二叉搜索树.md | 9 ++++++--- 1 file changed, 6 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 a271b977..cf8651f3 100644 --- a/problems/0098.验证二叉搜索树.md +++ b/problems/0098.验证二叉搜索树.md @@ -338,7 +338,7 @@ class Solution { Python： -**递归** - 利用BST中序遍历特性 +**递归** - 利用BST中序遍历特性,把树"压缩"成数组 ```python # Definition for a binary tree node. # class TreeNode: @@ -362,7 +362,7 @@ class Solution: def __is_sorted(nums: list) -> bool: for i in range(1, len(nums)): - if nums[i] <= nums[i - 1]: + if nums[i] <= nums[i - 1]: # ⚠️ 注意: Leetcode定义二叉搜索树中不能有重复元素 return False return True @@ -370,8 +370,11 @@ class Solution: res = __is_sorted(candidate_list) return res +``` -# 简单递归法 +**递归** - + +```python class Solution: def isValidBST(self, root: TreeNode) -> bool: def isBST(root, min_val, max_val): From 59fdafc7a116ca694b19ba78721bdc416cda76e8 Mon Sep 17 00:00:00 2001 From: Jack <965555169@qq.com> Date: Mon, 2 Aug 2021 08:58:19 +0800 Subject: [PATCH 08/14] =?UTF-8?q?=E6=B7=BB=E5=8A=A053.=E6=9C=80=E5=A4=A7?= =?UTF-8?q?=E5=AD=90=E5=BA=8F=E5=92=8C(=E5=8A=A8=E6=80=81=E8=A7=84?= =?UTF-8?q?=E5=88=92)-JavaScript=E7=89=88?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- .../0053.最大子序和（动态规划）.md | 17 +++++++++++++++++ 1 file changed, 17 insertions(+) diff --git a/problems/0053.最大子序和（动态规划）.md b/problems/0053.最大子序和（动态规划）.md index ada378b2..20a8c66c 100644 --- a/problems/0053.最大子序和（动态规划）.md +++ b/problems/0053.最大子序和（动态规划）.md @@ -168,6 +168,23 @@ func max(a,b int) int{ } ``` +JavaScript： + +```javascript +const maxSubArray = nums => { + // 数组长度，dp初始化 + const [len, dp] = [nums.length, [nums[0]]]; + // 最大值初始化为dp[0] + let max = dp[0]; + for (let i = 1; i < len; i++) { + dp[i] = Math.max(dp[i - 1] + nums[i], nums[i]); + // 更新最大值 + max = Math.max(max, dp[i]); + } + return max; +}; +``` + ----------------------- From 9a87b13fc3f87c1b46310d1c8da92b7b8ca8d078 Mon Sep 17 00:00:00 2001 From: Jack <965555169@qq.com> Date: Mon, 2 Aug 2021 09:16:10 +0800 Subject: [PATCH 09/14] =?UTF-8?q?=E6=B7=BB=E5=8A=A0392.=E5=88=A4=E6=96=AD?= =?UTF-8?q?=E5=AD=90=E5=BA=8F=E5=88=97(=E5=8A=A8=E6=80=81=E8=A7=84?= =?UTF-8?q?=E5=88=92)-JavaScript=E7=89=88?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- problems/0392.判断子序列.md | 25 ++++++++++++++++++++++++- 1 file changed, 24 insertions(+), 1 deletion(-) diff --git a/problems/0392.判断子序列.md b/problems/0392.判断子序列.md index d97d2684..09ee2c4d 100644 --- a/problems/0392.判断子序列.md +++ b/problems/0392.判断子序列.md @@ -180,7 +180,30 @@ class Solution: return False ``` -Go： +JavaScript： + +```javascript +const isSubsequence = (s, t) => { + // s、t的长度 + const [m, n] = [s.length, t.length]; + // dp全初始化为0 + const dp = new Array(m + 1).fill(0).map(x => new Array(n + 1).fill(0)); + for (let i = 1; i <= m; i++) { + for (let j = 1; j <= n; j++) { + // 更新dp[i][j]，两种情况 + if (s[i - 1] === t[j - 1]) { + dp[i][j] = dp[i - 1][j - 1] + 1; + } else { + dp[i][j] = dp[i][j - 1]; + } + } + } + // 遍历结束，判断dp右下角的数是否等于s的长度 + return dp[m][n] === m ? true : false; +}; +``` + + From 0fdede8c944b5052160370b3fe1241810021cfa3 Mon Sep 17 00:00:00 2001 From: Kelvin Date: Sun, 1 Aug 2021 22:53:23 -0400 Subject: [PATCH 10/14] =?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 将上一版本的代码改成跟题解思路相同. --- problems/0098.验证二叉搜索树.md | 26 +++++++++++++++++++------- 1 file changed, 19 insertions(+), 7 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 cf8651f3..a7634849 100644 --- a/problems/0098.验证二叉搜索树.md +++ b/problems/0098.验证二叉搜索树.md @@ -372,18 +372,30 @@ class Solution: return res ``` -**递归** - +**递归** - 标准做法 ```python class Solution: def isValidBST(self, root: TreeNode) -> bool: - def isBST(root, min_val, max_val): - if not root: return True - if root.val >= max_val or root.val <= min_val: + # 规律: BST的中序遍历节点数值是从小到大. + cur_max = -float("INF") + def __isValidBST(root: TreeNode) -> bool: + nonlocal cur_max + + if not root: + return True + + is_left_valid = __isValidBST(root.left) + if cur_max < root.val: + cur_max = root.val + else: return False - return isBST(root.left, min_val, root.val) and isBST(root.right, root.val, max_val) - return isBST(root, float("-inf"), float("inf")) - + is_right_valid = __isValidBST(root.right) + + return is_left_valid and is_right_valid + return __isValidBST(root) +``` +``` # 迭代-中序遍历 class Solution: def isValidBST(self, root: TreeNode) -> bool: From 152f7cc61a8e5891374b14c0ac998995fe3da767 Mon Sep 17 00:00:00 2001 From: Jack <965555169@qq.com> Date: Tue, 3 Aug 2021 08:45:05 +0800 Subject: [PATCH 11/14] =?UTF-8?q?=E6=B7=BB=E5=8A=A01035.=E4=B8=8D=E7=9B=B8?= =?UTF-8?q?=E4=BA=A4=E7=9A=84=E7=BA=BF-JavaScript=E7=89=88?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- problems/1035.不相交的线.md | 23 ++++++++++++++++++++++- 1 file changed, 22 insertions(+), 1 deletion(-) diff --git a/problems/1035.不相交的线.md b/problems/1035.不相交的线.md index cb74ef75..3a0e6a68 100644 --- a/problems/1035.不相交的线.md +++ b/problems/1035.不相交的线.md @@ -109,7 +109,28 @@ class Solution: return dp[-1][-1] ``` -Go： +JavaScript： + +```javascript +const maxUncrossedLines = (nums1, nums2) => { + // 两个数组长度 + const [m, n] = [nums1.length, nums2.length]; + // 创建dp数组并都初始化为0 + const dp = new Array(m + 1).fill(0).map(x => new Array(n + 1).fill(0)); + for (let i = 1; i <= m; i++) { + for (let j = 1; j <= n; j++) { + // 根据两种情况更新dp[i][j] + if (nums1[i - 1] === nums2[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]); + } + } + } + // 返回dp数组中右下角的元素 + return dp[m][n]; +}; +``` From 7cc60a02a7c62df1784ad9deca39cc7822f0e6e7 Mon Sep 17 00:00:00 2001 From: ltinyho Date: Tue, 3 Aug 2021 10:34:24 +0800 Subject: [PATCH 12/14] =?UTF-8?q?1002.=E6=9F=A5=E6=89=BE=E5=B8=B8=E7=94=A8?= =?UTF-8?q?=E5=AD=97=E7=AC=A6-JavaScript=E7=89=88?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- problems/1002.查找常用字符.md | 40 +++++++++++++++++++++++++++++ 1 file changed, 40 insertions(+) diff --git a/problems/1002.查找常用字符.md b/problems/1002.查找常用字符.md index 875340c4..e3014d00 100644 --- a/problems/1002.查找常用字符.md +++ b/problems/1002.查找常用字符.md @@ -169,6 +169,46 @@ class Solution { } } ``` +javaScript +```js +var commonChars = function (words) { + let res = [] + let size = 26 + let firstHash = new Array(size) + for (let i = 0; i < size; i++) { // 初始化 hash 数组 + firstHash[i] = 0 + } + + let a = "a".charCodeAt() + let firstWord = words[0] + for (let i = 0; i < firstWord.length; i++) { // 第 0 个单词的统计 + let idx = firstWord[i].charCodeAt() + firstHash[idx - a] += 1 + } + + for (let i = 1; i < words.length; i++) { // 1-n 个单词统计 + let otherHash = new Array(size) + for (let i = 0; i < size; i++) { // 初始化 hash 数组 + otherHash[i] = 0 + } + + for (let j = 0; j < words[i].length; j++) { + let idx = words[i][j].charCodeAt() + otherHash[idx - a] += 1 + } + for (let i = 0; i < size; i++) { + firstHash[i] = Math.min(firstHash[i], otherHash[i]) + } + } + for (let i = 0; i < size; i++) { + while (firstHash[i] > 0) { + res.push(String.fromCharCode(i + a)) + firstHash[i]-- + } + } + return res +}; +``` ----------------------- * 作者微信：[程序员Carl](https://mp.weixin.qq.com/s/b66DFkOp8OOxdZC_xLZxfw) From 4068040965153cbcbdd970be6abf5fa31be517f0 Mon Sep 17 00:00:00 2001 From: ltinyho Date: Tue, 3 Aug 2021 14:43:44 +0800 Subject: [PATCH 13/14] =?UTF-8?q?0018.=E5=9B=9B=E6=95=B0=E4=B9=8B=E5=92=8C?= =?UTF-8?q?-golang?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- problems/0018.四数之和.md | 48 +++++++++++++++++++++++++++++++++++ 1 file changed, 48 insertions(+) diff --git a/problems/0018.四数之和.md b/problems/0018.四数之和.md index 0caf12be..4a8fa947 100644 --- a/problems/0018.四数之和.md +++ b/problems/0018.四数之和.md @@ -201,6 +201,54 @@ class Solution(object): ``` Go： +```go +func fourSum(nums []int, target int) [][]int { + if len(nums) < 4 { + return nil + } + sort.Ints(nums) + var res [][]int + for i := 0; i < len(nums)-3; i++ { + n1 := nums[i] + // if n1 > target { // 不能这样写,因为可能是负数 + // break + // } + if i > 0 && n1 == nums[i-1] { + continue + } + for j := i + 1; j < len(nums)-2; j++ { + n2 := nums[j] + if j > i+1 && n2 == nums[j-1] { + continue + } + l := j + 1 + r := len(nums) - 1 + for l < r { + n3 := nums[l] + n4 := nums[r] + sum := n1 + n2 + n3 + n4 + if sum < target { + l++ + } else if sum > target { + r-- + } else { + res = append(res, []int{n1, n2, n3, n4}) + for l < r && n3 == nums[l+1] { // 去重 + l++ + } + for l < r && n4 == nums[r-1] { // 去重 + r-- + } + // 找到答案时,双指针同时靠近 + r-- + l++ + } + } + } + } + return res +} +``` javaScript: From 7ff7afcfaac673ba846cc5908aa68ee13d811fe0 Mon Sep 17 00:00:00 2001 From: YellowPeaches <326826436@qq.com> Date: Tue, 3 Aug 2021 16:25:05 +0800 Subject: [PATCH 14/14] =?UTF-8?q?update=200100=E7=9B=B8=E5=90=8C=E7=9A=84?= =?UTF-8?q?=E6=A0=91java=E7=89=88?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- problems/0100.相同的树.md | 16 ++++++++++++++++ 1 file changed, 16 insertions(+) diff --git a/problems/0100.相同的树.md b/problems/0100.相同的树.md index b536ffe3..c40f79fd 100644 --- a/problems/0100.相同的树.md +++ b/problems/0100.相同的树.md @@ -172,6 +172,22 @@ public: Java： +```java +class Solution { + public boolean isSameTree(TreeNode p, TreeNode q) { + if (p == null && q == null) { + return true; + } else if (q == null || p == null) { + return false; + } else if (q.val != p.val) { + return false; + } else { + return isSameTree(q.left, p.left) && isSameTree(q.right, p.right); + } + } +} + +``` Python： Go：