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给定一棵二叉树，想象自己站在它的右侧，按照从顶部到底部的顺序，返回从右侧所能看到的节点值。示例:输入: [1,2,3,null,5,null,4]输出: [1, 3, 4]解释:1 <—/ 2 3 <—\ 5 4 <—两种方法，bfs和dfsbfs：//bfs/** * Definition for a binary tree node. * struct TreeNode {

给定一组不含重复元素的整数数组 nums，返回该数组所有可能的子集（幂集）。说明：解集不能包含重复的子集。示例:输入: nums = [1,2,3]输出:[[3],[1],[2],[1,2,3],[1,3],[2,3],[1,2],[]]方法一：动态规划//动态规划class Solution {public: vector<vector<int>> subsets(vector<int>& nums) {

给定一个整数数组 nums ，找到一个具有最大和的连续子数组（子数组最少包含一个元素），返回其最大和。示例:输入: [-2,1,-3,4,-1,2,1,-5,4],输出: 6解释: 连续子数组 [4,-1,2,1] 的和最大，为 6。进阶:如果你已经实现复杂度为 O(n) 的解法，尝试使用更为精妙的分治法求解。方法一：dpclass Solution {public: int maxSubArray(vector<int>& nums) { in

在 O(n log n) 时间复杂度和常数级空间复杂度下，对链表进行排序。示例 1:输入: 4->2->1->3输出: 1->2->3->4示例 2:输入: -1->5->3->4->0输出: -1->0->3->4->5用归并排序解决，归并排序有两种写法，所以有两种方法。方法一：（迭代的归并排序）...

给定一个字符串，你需要反转字符串中每个单词的字符顺序，同时仍保留空格和单词的初始顺序。示例 1:输入: “Let’s take LeetCode contest”输出: “s’teL ekat edoCteeL tsetnoc”注意：在字符串中，每个单词由单个空格分隔，并且字符串中不会有任何额外的空格。方法一：（istringstream）//istringstream对象可以绑定一行...

给定一个整数，编写一个函数来判断它是否是 2 的幂次方。示例 1:输入: 1输出: true解释: 20 = 1示例 2:输入: 16输出: true解释: 24 = 16示例 3:输入: 218输出: false方法一：log函数：若底数为m，则为log(n)/log(m)pow函数： pow(2,3)=2^3round: 四舍五入取整class Solution...

Given an unsorted array of integers, find the length of longest increasing subsequence.Example:Input: [10,9,2,5,3,7,101,18]Output: 4Explanation: The longest increasing subsequence is [2,3,7,101], ...

Given a binary tree, determine if it is a valid binary search tree (BST).Assume a BST is defined as follows:The left subtree of a node contains only nodes with keys less than the node’s key.The rig...

Given a binary search tree (BST) with duplicates, find all the mode(s) (the most frequently occurred element) in the given BST.Assume a BST is defined as follows:The left subtree of a node contains ...

Given two words word1 and word2, find the minimum number of operations required to convert word1 to word2.You have the following 3 operations permitted on a word:Insert a characterDelete a characte...

Given a binary search tree, write a function kthSmallest to find the kth smallest element in it.Note:You may assume k is always valid, 1 ≤ k ≤ BST’s total elements.Example 1:Input: root = [3,1,4,n...

Given a binary tree, find the lowest common ancestor (LCA) of two given nodes in the tree.According to the definition of LCA on Wikipedia: “The lowest common ancestor is defined between two nodes p a...

Assume you are an awesome parent and want to give your children some cookies. But, you should give each child at most one cookie. Each child i has a greed factor gi, which is the minimum size of a coo...

Given n, how many structurally unique BST’s (binary search trees) that store values 1 … n?Example:Input: 3Output: 5Explanation:Given n = 3, there are a total of 5 unique BST’s:1 3 3 ...

The demons had captured the princess § and imprisoned her in the bottom-right corner of a dungeon. The dungeon consists of M x N rooms laid out in a 2D grid. Our valiant knight (K) was initially posit...

Given a m x n grid filled with non-negative numbers, find a path from top left to bottom right which minimizes the sum of all numbers along its path.Note: You can only move either down or right at an...

Given a triangle, find the minimum path sum from top to bottom. Each step you may move to adjacent numbers on the row below.For example, given the following triangle[[2],[3,4],[6,5,7],[4,1,8,3]...

Given an integer array nums, find the contiguous subarray (containing at least one number) which has the largest sum and return its sum.Example:Input: [-2,1,-3,4,-1,2,1,-5,4],Output: 6Explanation:...

You are a professional robber planning to rob houses along a street. Each house has a certain amount of money stashed, the only constraint stopping you from robbing each of them is that adjacent house...

You are climbing a stair case. It takes n steps to reach to the top.Each time you can either climb 1 or 2 steps. In how many distinct ways can you climb to the top?Note: Given n will be a positive i...

Remove all elements from a linked list of integers that have value val.Example:Input: 1->2->6->3->4->5->6, val = 6Output: 1->2->3->4->5大意：移除等于val的元素（可能不止一个）方法：遍历链表，...

Say you have an array for which the ith element is the price of a given stock on day i.Design an algorithm to find the maximum profit. You may complete as many transactions as you like (i.e., buy one...

Given a binary tree, return the preorder traversal of its nodes’ values.Example:Input: [1,null,2,3]12/3Output: [1,2,3]Follow up: Recursive solution is trivial, could you do it iteratively?大意...

Given a binary tree, flatten it to a linked list in-place.For example, given the following tree:1/ 2 5/ \ 3 4 6The flattened tree should look like:123456大意：将二叉树展开为链表方法：有两种展...

Given an array of non-negative integers, you are initially positioned at the first index of the array.Each element in the array represents your maximum jump length at that position.Determine if you ...

Given a binary tree and a sum, find all root-to-leaf paths where each path’s sum equals the given sum.Note: A leaf is a node with no children.Example:Given the below binary tree and sum = 22, 5 ...

Given a binary tree and a sum, determine if the tree has a root-to-leaf path such that adding up all the values along the path equals the given sum.Note: A leaf is a node with no children.Example:G...

Given a linked list, rotate the list to the right by k places, where k is non-negative.Example 1:Input: 1->2->3->4->5->NULL, k = 2Output: 4->5->1->2->3->NULLExplanati...

Reverse a linked list from position m to n. Do it in one-pass.Note: 1 ≤ m ≤ n ≤ length of list.Example:Input: 1->2->3->4->5->NULL, m = 2, n = 4Output: 1->4->3->2->5->...

Reverse a singly linked list.Example:Input: 1->2->3->4->5->NULLOutput: 5->4->3->2->1->NULLFollow up:A linked list can be reversed either iteratively or recursively. ...

Given a binary tree, imagine yourself standing on the right side of it, return the values of the nodes you can see ordered from top to bottom.Example:Input: [1,2,3,null,5,null,4]Output: [1, 3, 4]E...

Given a binary tree, return the bottom-up level order traversal of its nodes’ values. (ie, from left to right, level by level from leaf to root).For example:Given binary tree [3,9,20,null,null,15,7]...

Given a binary tree, find its maximum depth.The maximum depth is the number of nodes along the longest path from the root node down to the farthest leaf node.Note: A leaf is a node with no children....

Given a binary tree, return the level order traversal of its nodes’ values. (ie, from left to right, level by level).For example:Given binary tree [3,9,20,null,null,15,7],3/ 9 20/ 15 7retu...

Given two binary trees, write a function to check if they are the same or not.Two binary trees are considered the same if they are structurally identical and the nodes have the same value.Example 1:...

Given a binary tree, return the inorder traversal of its nodes’ values.Example:Input: [1,null,2,3]12/3Output: [1,3,2]Follow up: Recursive solution is trivial, could you do it iteratively?*中文...