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Word BreakGiven a non-empty string s and a dictionary wordDict containing a list of non-empty words, determine if s can be segmented into a space-separated sequence of one or more dictionary words.N...

Minimum Window SubstringGiven 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”Ou...

Edit DistanceGiven 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 characterDel...

Scramble StringGiven a string s1, we may represent it as a binary tree by partitioning it to two non-empty substrings recursively.Below is one possible representation of s1 = “great”:Given two str...

SubsetsGiven a set of distinct integers, nums, return all possible subsets (the power set).Note: The solution set must not contain duplicate subsets.Example:Input: nums = [1,2,3]Output:[[3],[...

Restore IP AddressesGiven a string containing only digits, restore it by returning all possible valid IP address combinations.Example:Input: “25525511135”Output: [“255.255.11.135”, “255.255.111.3...

Largest Rectangle in HistogramGiven n non-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.Example:I...

Find First and Last Position of Element in Sorted ArrayGiven an array of integers nums sorted in ascending order, find the starting and ending position of a given target value.Your algorithm’s runti...

N-QueensThe 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, return all distinct solutions to the n-queens puzzle...

Maximal SquareGiven a 2D binary matrix filled with 0’s and 1’s, find the largest square containing only 1’s and return its area.Example:Input:1 0 1 0 01 0 1 1 11 1 1 1 11 0 0 1 0Output: 4解法...

Interleaving StringGiven 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 =...

CandyThere are N children standing in a line. Each child is assigned a rating value.You are giving candies to these children subjected to the following requirements:Each child must have at least on...

Palindrome Partitioning IIGiven 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:Input:...

Palindrome PartitioningGiven a string s, partition s such that every substring of the partition is a palindrome.Return all possible palindrome partitioning of s.Example:Input: “aab”Output:[[“a...

Longest Consecutive SequenceGiven 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...

Surrounded RegionsGiven a 2D board containing ‘X’ and ‘O’ (the letter O), capture all regions surrounded by ‘X’.A region is captured by flipping all 'O’s into 'X’s in that surrounded region.Example...

Max Points on a LineGiven n points on a 2D plane, find the maximum number of points that lie on the same straight line.Example 1:Input: [[1,1],[2,2],[3,3]]Output: 3Explanation:^|| o| ...

Word LadderGiven 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 chan...

Distinct SubsequencesGiven a string S and a string T, count the number of distinct subsequences of S which equals T.A subsequence of a string is a new string which is formed from the original string...

Search in Rotated Sorted ArraySuppose an array sorted in ascending order is rotated at some pivot unknown to you beforehand.(i.e., [0,1,2,4,5,6,7] might become [4,5,6,7,0,1,2]).You are given a targ...

Permutations 2Given a collection of numbers that might contain duplicates, return all possible unique permutations.Example:Input: [1,1,2]Output:[[1,1,2],[1,2,1],[2,1,1]]解析相比于Permutations，...

Longest Valid ParenthesesGiven a string containing just the characters ‘(’ and ‘)’, find the length of the longest valid (well-formed) parentheses substring.Example 1:Input: “(()”Output: 2Explan...

Two SumGiven an array of integers, return indices of the two numbers such that they add up to a specific target.You may assume that each input would have exactly one solution, and you may not use th...

4SumGiven an array nums of n integers and an integer target, are there elements a, b, c, and d in nums such that a + b + c + d = target? Find all unique quadruplets in the array which gives the sum o...

3Sum ClosestGiven an array nums of n integers and an integer target, find three integers in nums such that the sum is closest to target. Return the sum of the three integers. You may assume that each...

3SumGiven an array nums of n integers, are there elements a, b, c in nums such that a + b + c = 0? Find all unique triplets in the array which gives the sum of zero.Note:The solution set must not c...

First Missing PositiveGiven an unsorted integer array, find the smallest missing positive integer.Example 1:Input: [1,2,0]Output: 3Example 2:Input: [3,4,-1,1]Output: 2Example 3:Input: [7...

Sudoku SolverWrite a program to solve a Sudoku puzzle by filling the empty cells.A sudoku solution must satisfy all of the following rules:Each of the digits 1-9 must occur exactly once in each ro...

Regular Expression MatchingGiven an input string (s) and a pattern §, implement regular expression matching with support for ‘.’ and ‘*’.‘.’ Matches any single character.‘*’ Matches zero or more o...

Longest Palindromic SubstringGiven a string s, find the longest palindromic substring in s. You may assume that the maximum length of s is 1000.Example 1:Input: “babad”Output: “bab”Note: “aba” i...

Longest Substring Without Repeating CharactersGiven a string, find the length of the longest substring without repeating characters.Example 1:Input: “abcabcbb”Output: 3Explanation: The answer is...

Letter Combinations of a Phone NumberGiven a string containing digits from 2-9 inclusive, return all possible letter combinations that the number could represent.A mapping of digit to letters (just ...

Divide Two IntegersGiven two integers dividend and divisor, divide two integers without using multiplication, division and mod operator.Return the quotient after dividing dividend by divisor.The in...

PermutationsGiven a collection of distinct integers, return all possible permutations.Example:Input: [1,2,3]Output:[[1,2,3],[1,3,2],[2,1,3],[2,3,1],[3,1,2],[3,2,1]]解析生成全排列。解法1：DFS用一个...

Jump Game2Given 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.Your g...

Jump GameGiven 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.Determi...

Best Time to Buy and Sell Stock IIISay 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 at most two...

Multiply StringsGiven two non-negative integers num1 and num2 represented as strings, return the product of num1 and num2, also represented as a string.Example 1:Input: num1 = “2”, num2 = “3”Outp...

Generate ParenthesesGiven n pairs of parentheses, write a function to generate all combinations of well-formed parentheses.For example, given n = 3, a solution set is:[“((()))”,“(()())”,“(())()...

Trapping Rain WaterGiven n non-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.Example:Input: [0,1,0,2,1,...