天行健，君子以自强不息

Given a binary tree containing digits from 0-9 only, each root-to-leaf path could represent a number.An example is the root-to-leaf path 1->2->3 which represents the number 123.Find the tota...

Given two words (beginWord and endWord), and a dictionary's word list, find the length of shortest transformation sequence from beginWord to endWord, such that:Only one letter can be changed at a ti...

A message containing letters from A-Z is being encoded to numbers using the following mapping:'A' -> 1'B' -> 2...'Z' -> 26Given a non-empty string containing only digits, determine t...

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 ...

Given s1, s2, s3, find whether s3 is formed by the interleaving of s1 and s2.Example 1:Input: s1 = "aabcc", s2 = "dbbca", s3 = "aadbbcbcac"Output: trueExample 2:Input: s1 = "aabcc", s2 = "...

Given two sorted integer arrays nums1 and nums2, merge nums2 into nums1 as one sorted array.Note:The number of elements initialized in nums1 and nums2 are m and n respectively. You may assume tha...

Write an efficient algorithm that searches for a value in an m x n matrix. This matrix has the following properties:Integers in each row are sorted from left to right. The first integer of each row...

Write an efficient algorithm that searches for a value in an m x n matrix. This matrix has the following properties:Integers in each row are sorted in ascending from left to right. Integers in each...

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 character Delete a chara...

Given a binary tree, check whether it is a mirror of itself (ie, symmetric around its center).For example, this binary tree is symmetric: 1 / \ 2 2 / \ / \3 4 4 3 But the follo...

题解：就是用中序和后序重建二叉树保证每个点不重复值上这里顺便列下中序和先序的代码，思路都一样用map存储可以节省查找时间，注意边界处理class Solution {private: unordered_map<int, int> inm; // inorder map [inorder[i], i]public: TreeNode* build...

Given a collection of integers that might contain duplicates, nums, return all possible subsets (the power set).Note: The solution set must not contain duplicate subsets.Example:Input: [1,2,2]...

Given an unsorted array of integers, find the length of the longest consecutive elements sequence.Your algorithm should run in O(n) complexity.Example:Input: [100, 4, 200, 1, 3, 2]Output: 4Ex...

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...

Given two words (beginWord and endWord), and a dictionary's word list, find all shortest transformation sequence(s) from beginWord to endWord, such that:Only one letter can be changed at a time Eac...

 Given a singly linked list where elements are sorted in ascending order, convert it to a height balanced BST.题解：给定一个链表有序的转成平衡BST，关键这里我用额外空间MLE所以应该在链表上直接进行，最优化的应该是设计两个指针，一个slow一个fast用来遍历中间节点，然后左右子...

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 ...

Given a string containing only digits, restore it by returning all possible valid IP address combinations.Example:Input: "25525511135"Output: ["255.255.11.135", "255.255.111.35"]题解：递归判断是不是合法ip...

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-...

Given a m x n matrix, if an element is 0, set its entire row and column to 0. Do it in-place.Example 1:Input: [  [1,1,1],  [1,0,1],  [1,1,1]]Output: [  [1,0,1],  [0,0,0],  [1,0,1]]E...

Given two integers n and k, return all possible combinations of k numbers out of 1 ... n.Example:Input: n = 4, k = 2Output:[ [2,4], [3,4], [2,3], [1,2], [1,3], [1,4],]题解：三种解法，最直接...

Given a 2D board and a word, find if the word exists in the grid.The word can be constructed from letters of sequentially adjacent cell, where "adjacent" cells are those horizontally or vertically n...

给定一个字符串 s ，找出至多包含两个不同字符的最长子串 t 。示例 1:输入: "eceba"输出: 3解释: t 是 "ece"，长度为3。示例 2:输入: "ccaabbb"输出: 5解释: t 是 "aabbb"，长度为5。来源：力扣（LeetCode）链接：https://leetcode-cn.com/problems/longest-substrin...

In a row of trees, the i-th tree produces fruit with type tree[i].You start at any tree of your choice, then repeatedly perform the following steps:Add one piece of fruit from this tree to your b...

Given an array nums, there is a sliding window of size k which is moving from the very left of the array to the very right. You can only see the k numbers in the window. Each time the sliding window ...

Givennnon-negative integersa1,a2, ...,an, where each represents a point at coordinate (i,ai).nvertical lines are drawn such that the two endpoints of lineiis at (i,ai) and (i, 0). Find two...

Givennnon-negative integers representing the histogram's bar height where the width of each bar is 1, find the area of largest rectangle in the histogram.Above is a histogram where width of ea...

Givennnon-negative integers representing an elevation map where the width of each bar is 1, compute how much water it is able to trap after raining.The above elevation map is represented by array...

Write a classStockSpannerwhich collects daily price quotes for some stock, and returns thespanof that stock's price for the current day.The span of the stock's price todayis defined as the maxi...

Given a list of daily temperaturesT, return a list such that, for each day in the input, tells you how many days you would have to wait until a warmer temperature. If there is no future day for which...

Given a string S and a string T, find the minimum window in S which will contain all the characters in T in complexity O(n).Example:Input: S = "ADOBECODEBANC", T = "ABC"Output: "BANC"Note:I...

Your are given an array of positive integers nums.Count and print the number of (contiguous) subarrays where the product of all the elements in the subarray is less than k.Example 1:Input: nums ...

Return the length of the shortest, non-empty, contiguous subarray of A with sum at least K.If there is no non-empty subarray with sum at least K, return -1. Example 1:Input: A = [1], K = 1Ou...

Given a linked list and a value x, partition it such that all nodes less than x come before nodes greater than or equal to x.You should preserve the original relative order of the nodes in each of t...

Given a 2D board and a list of words from the dictionary, find all words in the board.Each word must be constructed from letters of sequentially adjacent cell, where "adjacent" cells are those horiz...

Given a 2D binary matrix filled with 0's and 1's, find the largest rectangle containing only 1's and return its area.Example:Input:[ ["1","0","1","0","0"], ["1","0","1&quo

编写一个 SQL 查询，查找Person 表中所有重复的电子邮箱。示例：+----+---------+| Id | Email |+----+---------+| 1 | a@b.com || 2 | c@d.com || 3 | a@b.com |+----+---------+根据以上输入，你的查询应返回以下结果：+---------+| Emai...

我们将给定的数组A分成K个相邻的非空子数组 ，我们的分数由每个子数组内的平均值的总和构成。计算我们所能得到的最大分数是多少。注意我们必须使用 A 数组中的每一个数进行分组，并且分数不一定需要是整数。示例:输入: A = [9,1,2,3,9]K = 3输出: 20解释: A 的最优分组是[9], [1, 2, 3], [9]. 得到的分数是 9 + (1 + 2 + ...

在一个长度无限的数轴上，第 i 颗石子的位置为stones[i]。如果一颗石子的位置最小/最大，那么该石子被称作端点石子。每个回合，你可以将一颗端点石子拿起并移动到一个未占用的位置，使得该石子不再是一颗端点石子。值得注意的是，如果石子像stones = [1,2,5]这样，你将无法移动位于位置 5 的端点石子，因为无论将它移动到任何位置（例如 0 或 3），该石子都仍然会是端点石子...