James Pan

原题网址：https://leetcode.com/problems/matchsticks-to-square/Remember the story of Little Match Girl? By now, you know exactly what matchsticks the little match girl has, please find out a way you c

原题网址：https://leetcode.com/problems/word-search/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

原题网址：https://leetcode.com/problems/combinations/Given two integers n and k, return all possible combinations of k numbers out of 1 ... n.For example,If n = 4 and k = 2, a solution is:[

原题网址：https://leetcode.com/problems/water-and-jug-problem/You are given two jugs with capacities x and y litres. There is an infinite amount of water supply available. You need to determine wheth

一个长度为n的数组，从中选取k个数字，若定义这k个数字的半径为排序后相邻两个数字之间的最小间隔，则k个数字所能达到的最大半径是多少？如果k = 1，则半径为无穷大。假设k > 0。方法一：深度优先搜索。class SolutionDFS { private int max = 0; public SolutionDFS(int[] nums, int k) { find(n

原题网址：https://leetcode.com/problems/n-queens-ii/Follow up for N-Queens problem.Now, instead outputting board configurations, return the total number of distinct solutions.方法一：深度优先搜索，使用一

原题网址：https://leetcode.com/problems/permutations/Given a collection of distinct numbers, return all possible permutations.For example,[1,2,3] have the following permutations:[1,2,3], [1,3

原题网址：https://leetcode.com/problems/combination-sum-ii/Given a collection of candidate numbers (C) and a target number (T), find all unique combinations in C where the candidate numbers sums to

原题网址：https://leetcode.com/problems/combination-sum/Given a set of candidate numbers (C) and a target number (T), find all unique combinations in C where the candidate numbers sums to T.The

原题网址：https://leetcode.com/problems/sudoku-solver/Write a program to solve a Sudoku puzzle by filling the empty cells.Empty cells are indicated by the character '.'.You may assume that th

原题网址：https://leetcode.com/problems/letter-combinations-of-a-phone-number/Given a digit string, return all possible letter combinations that the number could represent.A mapping of digit to l

原题网址：https://leetcode.com/problems/word-break-ii/Given a string s and a dictionary of words dict, add spaces in s to construct a sentence where each word is a valid dictionary word.Return al

原题网址：https://leetcode.com/problems/scramble-string/Given a string s1, we may represent it as a binary tree by partitioning it to two non-empty substrings recursively.Below is one possible

原题网址：https://leetcode.com/problems/subsets-ii/Given a collection of integers that might contain duplicates, nums, return all possible subsets.Note:Elements in a subset must be in non-d

原题网址：https://leetcode.com/problems/n-queens/The n-queens puzzle is the problem of placing n queens on an n×n chessboard such that no two queens attack each other.Given an integer n, retu

原题网址：https://leetcode.com/problems/minimum-height-trees/For a undirected graph with tree characteristics, we can choose any node as the root. The result graph is then a rooted tree. Among all po

原题网址：https://leetcode.com/problems/alien-dictionary/There is a new alien language which uses the latin alphabet. However, the order among letters are unknown to you. You receive a list of words

原题网址：https://leetcode.com/problems/integer-break/Given a positive integer n, break it into the sum of at least two positive integers and maximize the product of those integers. Return the maximu

原题网址：https://leetcode.com/problems/reconstruct-itinerary/Given a list of airline tickets represented by pairs of departure and arrival airports [from, to], reconstruct the itinerary in order.

原题网址：https://leetcode.com/problems/generate-parentheses/Given n pairs of parentheses, write a function to generate all combinations of well-formed parentheses.For example, given n = 3, a sol

原题网址：https://leetcode.com/problems/word-search-ii/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 sequenti

原题网址：https://leetcode.com/problems/word-pattern-ii/Given a pattern and a string str, find if str follows the same pattern.Here follow means a full match, such that there is a bijection bet

原题网址：https://leetcode.com/problems/palindrome-pairs/Given a list of unique words. Find all pairs of distinct indices (i, j) in the given list, so that the concatenation of the two words, i.e.

原题网址：https://leetcode.com/problems/restore-ip-addresses/Given a string containing only digits, restore it by returning all possible valid IP address combinations.For example:Given "2552551

原题网址：https://leetcode.com/problems/strobogrammatic-number-iii/A strobogrammatic number is a number that looks the same when rotated 180 degrees (looked at upside down).Write a function to co

原题网址：https://leetcode.com/problems/combination-sum-iii/Find all possible combinations of k numbers that add up to a number n, given that only numbers from 1 to 9 can be used and each combinati

原题网址：https://leetcode.com/problems/palindrome-permutation-ii/Given a string s, return all the palindromic permutations (without duplicates) of it. Return an empty list if no palindromic permut

原题网址：https://leetcode.com/problems/graph-valid-tree/Given n nodes labeled from 0 to n - 1 and a list of undirected edges (each edge is a pair of nodes), write a function to check whether these

原题网址：https://leetcode.com/problems/binary-tree-paths/Given a binary tree, return all root-to-leaf paths.For example, given the following binary tree: 1 / \2 3 \ 5

原题网址：https://leetcode.com/problems/flip-game-ii/You are playing the following Flip Game with your friend: Given a string that contains only these two characters: + and -, you and your friend t

原题网址：https://leetcode.com/problems/path-sum-ii/Given a binary tree and a sum, find all root-to-leaf paths where each path's sum equals the given sum.For example:Given the below binary tree

原题网址：https://leetcode.com/problems/maximum-depth-of-binary-tree/Given a binary tree, find its maximum depth.The maximum depth is the number of nodes along the longest path from the root node

原题网址：https://leetcode.com/problems/factor-combinations/Numbers can be regarded as product of its factors. For example,8 = 2 x 2 x 2; = 2 x 4.Write a function that takes an integer n and

原题网址：https://leetcode.com/problems/longest-increasing-path-in-a-matrix/Given an integer matrix, find the length of the longest increasing path.From each cell, you can either move to four dir

原题网址：https://leetcode.com/problems/walls-and-gates/You are given a m x n 2D grid initialized with these three possible values.-1 - A wall or an obstacle.0 - A gate.INF - Infinity means an em

原题网址：https://leetcode.com/problems/expression-add-operators/Given a string that contains only digits 0-9 and a target value, return all possibilities to add binary operators (not unary) +, -,

原题网址：https://leetcode.com/problems/android-unlock-patterns/Given an Android 3x3 key lock screen and two integers m and n, where 1 ≤ m ≤ n ≤ 9, count the total number of unlock patterns of the An

原题网址：https://leetcode.com/problems/subsets/Given a set of distinct integers, nums, return all possible subsets.Note:Elements in a subset must be in non-descending order.The solution se

原题网址：https://leetcode.com/problems/serialize-and-deserialize-binary-tree/Serialization is the process of converting a data structure or object into a sequence of bits so that it can be stored in

原题网址：https://leetcode.com/problems/add-and-search-word-data-structure-design/Design a data structure that supports the following two operations:void addWord(word)bool search(word)search(