原文链接: https://leetcode-cn.com/problems/path-sum 英文原文Given the root of a binary tree and an integer targetSum, return true if the tree has a root-to-leaf path such that adding up all the values along the path equals targetSum. A leaf is a node with no…

原文链接: https://leetcode-cn.com/problems/path-sum-ii 英文原文Given the root of a binary tree and an integer targetSum, return all root-to-leaf paths where the sum of the node values in the path equals targetSum. Each path should be returned as a list of th…

原文链接: https://leetcode-cn.com/problems/distinct-subsequences 英文原文Given two strings s and t, return the number of distinct subsequences of s which equals t. A string's subsequence is a new string formed from the original string by deleting some (can b…

原文链接: https://leetcode-cn.com/problems/populating-next-right-pointers-in-each-node 英文原文You are given a perfect binary tree where all leaves are on the same level, and every parent has two children. The binary tree has the following definition: struct…

原文链接: https://leetcode-cn.com/problems/populating-next-right-pointers-in-each-node-ii 英文原文Given a binary tree struct Node { int val; Node *left; Node *right; Node *next; } Populate each next pointer to point to its next right node. If there is no nex…

原文链接: https://leetcode-cn.com/problems/pascals-triangle 英文原文Given an integer numRows, return the first numRows of Pascal's triangle. In Pascal's triangle, each number is the sum of the two numbers directly above it as shown: Example 1: Input: numRows…

原文链接: https://leetcode-cn.com/problems/pascals-triangle-ii 英文原文Given an integer rowIndex, return the rowIndexth (0-indexed) row of the Pascal's triangle. In Pascal's triangle, each number is the sum of the two numbers directly above it as shown: Exam…

原文链接: https://leetcode-cn.com/problems/triangle 英文原文Given a triangle array, return the minimum path sum from top to bottom. For each step, you may move to an adjacent number of the row below. More formally, if you are on index i on the current row, y…

原文链接: https://leetcode-cn.com/problems/best-time-to-buy-and-sell-stock 英文原文You are given an array prices where prices[i] is the price of a given stock on the ith day. You want to maximize your profit by choosing a single day to buy one stock and choo…

原文链接: https://leetcode-cn.com/problems/best-time-to-buy-and-sell-stock-iii 英文原文You are given an array prices where prices[i] is the price of a given stock on the ith day. Find the maximum profit you can achieve. You may complete at most two transacti…

原文链接: https://leetcode-cn.com/problems/best-time-to-buy-and-sell-stock-ii 英文原文You are given an integer array prices where prices[i] is the price of a given stock on the ith day. On each day, you may decide to buy and/or sell the stock. You can only h…

原文链接: https://leetcode-cn.com/problems/binary-tree-maximum-path-sum 英文原文A path in a binary tree is a sequence of nodes where each pair of adjacent nodes in the sequence has an edge connecting them. A node can only appear in the sequence at most once.…

原文链接: https://leetcode-cn.com/problems/word-ladder-ii 英文原文A transformation sequence from word beginWord to word endWord using a dictionary wordList is a sequence of words beginWord -> s1 -> s2 -> ... -> sk such that: Every adjacent pair of words diff…

原文链接: https://leetcode-cn.com/problems/word-ladder 英文原文A transformation sequence from word beginWord to word endWord using a dictionary wordList is a sequence of words beginWord -> s1 -> s2 -> ... -> sk such that: Every adjacent pair of words differs…

原文链接: https://leetcode-cn.com/problems/longest-consecutive-sequence 英文原文Given an unsorted array of integers nums, return the length of the longest consecutive elements sequence. You must write an algorithm that runs in O(n) time. Example 1: Input: nu…

原文链接: https://leetcode-cn.com/problems/sum-root-to-leaf-numbers 英文原文You are given the root of a binary tree containing digits from 0 to 9 only. Each root-to-leaf path in the tree represents a number. For example, the root-to-leaf path 1 -> 2 -> 3 rep…

原文链接: https://leetcode-cn.com/problems/surrounded-regions 英文原文Given an m x n matrix board containing 'X' and 'O', capture all regions that are 4-directionally surrounded by 'X'. A region is captured by flipping all 'O's into 'X's in that surrounded r…

原文链接: https://leetcode-cn.com/problems/palindrome-partitioning 英文原文Given a string s, partition s such that every substring of the partition is a palindrome. Return all possible palindrome partitioning of s. A palindrome string is a string that reads …

原文链接: https://leetcode-cn.com/problems/palindrome-partitioning-ii 英文原文Given a string s, partition s such that every substring of the partition is a palindrome. Return the minimum cuts needed for a palindrome partitioning of s. Example 1: Input: s = "…

原文链接: https://leetcode-cn.com/problems/clone-graph 英文原文Given a reference of a node in a connected undirected graph. Return a deep copy (clone) of the graph. Each node in the graph contains a value (int) and a list (List[Node]) of its neighbors. class…

原文链接: https://leetcode-cn.com/problems/gas-station 英文原文There are n gas stations along a circular route, where the amount of gas at the ith station is gas[i]. You have a car with an unlimited gas tank and it costs cost[i] of gas to travel from the ith…

原文链接: https://leetcode-cn.com/problems/candy 英文原文There are n children standing in a line. Each child is assigned a rating value given in the integer array ratings. You are giving candies to these children subjected to the following requirements: Each…

原文链接: https://leetcode-cn.com/problems/flatten-binary-tree-to-linked-list 英文原文Given the root of a binary tree, flatten the tree into a "linked list": The "linked list" should use the same TreeNode class where the right child pointer points to the nex…

原文链接: https://leetcode-cn.com/problems/valid-palindrome 英文原文A phrase is a palindrome if, after converting all uppercase letters into lowercase letters and removing all non-alphanumeric characters, it reads the same forward and backward. Alphanumeric …

原文链接: https://leetcode-cn.com/problems/single-number 英文原文Given a non-empty array of integers nums, every element appears twice except for one. Find that single one. You must implement a solution with a linear runtime complexity and use only constant …

原文链接: https://leetcode-cn.com/problems/copy-list-with-random-pointer 英文原文A linked list of length n is given such that each node contains an additional random pointer, which could point to any node in the list, or null. Construct a deep copy of the li…

原文链接: https://leetcode-cn.com/problems/word-break 英文原文Given a string s and a dictionary of strings wordDict, return true if s can be segmented into a space-separated sequence of one or more dictionary words. Note that the same word in the dictionary …

原文链接: https://leetcode-cn.com/problems/word-break-ii 英文原文Given a string s and a dictionary of strings wordDict, add spaces in s to construct a sentence where each word is a valid dictionary word. Return all such possible sentences in any order. Note …

原文链接: https://leetcode-cn.com/problems/linked-list-cycle 英文原文Given head, the head of a linked list, determine if the linked list has a cycle in it. There is a cycle in a linked list if there is some node in the list that can be reached again by conti…

原文链接: https://leetcode-cn.com/problems/linked-list-cycle-ii 英文原文Given the head of a linked list, return the node where the cycle begins. If there is no cycle, return null. There is a cycle in a linked list if there is some node in the list that can b…