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Divide two integers without using multiplication, division and mod operator.If it is overflow, return MAX_INT.刚看这一题时确实没什么思路，还想着一直减减减，后来看到tags里有二分查找，就有思路了。amazing比如说 25/3 这一题，用一个Map存上（3-1）（6-

Given a collection of candidate numbers (C) and a target number (T), find all unique combinations in C where the candidate numbers sums to T.Each number in C may only be used once in the combina

Given an unsorted integer array, find the first missing positive integer.For example,Given [1,2,0] return 3,and [3,4,-1,1] return 2.Your algorithm should run in O(n) time and uses constant

Given 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.For example, Given [0,1,0,2,1,0,1,3,2,1,2,1]

Given two numbers represented as strings, return multiplication of the numbers as a string.Note:The numbers can be arbitrarily large and are non-negative.Converting the input string to integ

Implement wildcard pattern matching with support for '?' and '*'.'?' Matches any single character.'*' Matches any sequence of characters (including the empty sequence).The matching should cover t

Given an array of words and a length L, format the text such that each line has exactly L characters and is fully (left and right) justified.You should pack your words in a greedy approach; that i

Implement int sqrt(int x).Compute and return the square root of x.这道题么，当然最简单的方法就是一行代码  return（int）Math.sqrt(x);不过出于强迫症，还是用二分法又写了一遍代码。需要注意的地方是循环应该是while(left public int mySq

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.Your goal i

Given a collection of distinct numbers, return all possible permutations.For example,[1,2,3] have the following permutations:[ [1,2,3], [1,3,2], [2,1,3], [2,3,1], [3,1,2],

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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 same repeated number may be chosen from C unlimited numb

Given a string containing just the characters '(' and ')', find the length of the longest valid (well-formed) parentheses substring.For "(()", the longest valid parentheses substring is "()",

这道题Hard模式，比较复杂，又没有用到很经典的算法，卡在这道题很长时间了。首先比较直观的解法package datastru;import java.util.ArrayList;import java.util.HashMap;import java.util.List;import java.util.Map;public class Solution {

Suppose a sorted array 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 target value to search. If found in the array retur

Implement next permutation, which rearranges numbers into the lexicographically next greater permutation of numbers.If such arrangement is not possible, it must rearrange it as the lowest possible

Given a sorted array of integers, find the starting and ending position of a given target value.Your algorithm's runtime complexity must be in the order of O(log n).If the target is not found

Given a sorted array and a target value, return the index if the target is found. If not, return the index where it would be if it were inserted in order.You may assume no duplicates in the array.

Determine if a Sudoku is valid, according to: Sudoku Puzzles - The Rules.The Sudoku board could be partially filled, where empty cells are filled with the character '.'.A partially fille

Additive number is a string whose digits can form additive sequence.A valid additive sequence should contain at least three numbers. Except for the first two numbers, each subsequent number in the

Write a program to solve a Sudoku puzzle by filling the empty cells.Empty cells are indicated by the character '.'.You may assume that there will be only one unique solution.A sudoku

Given a collection of numbers that might contain duplicates, return all possible unique permutations.For example,[1,1,2] have the following unique permutations:[ [1,1,2], [1,2,1], [2,1,1

You are given an n x n 2D matrix representing an image.Rotate the image by 90 degrees (clockwise).Follow up:Could you do this in-place?这道题木有什么难度，原地顺时针旋转一个矩阵90度，要求时间复杂度O（n2），空间复杂度

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?这道题是一个比较经典比较简单的问题。

Given an integer n, generate a square matrix filled with elements from 1 to n2 in spiral order.For example,Given n = 3,You should return the following matrix:[ [ 1, 2, 3 ], [ 8, 9, 4 ], [

The set [1,2,3,…,n] contains a total of n! unique permutations.By listing and labeling all of the permutations in order,We get the following sequence (ie, for n = 3):"123""132""213""231""3

Given two words word1 and word2, find the minimum number of steps required to convert word1 to word2. (each operation is counted as 1 step.)You have the following 3 operations permitted on a word:

Given a list, rotate the list to the right by k places, where k is non-negative.For example:Given 1->2->3->4->5->NULL and k = 2,return 4->5->1->2->3->NULL.这道题也不是很难。循环右移一个链表。要注意的是循环的位数可能会

A robot is located at the top-left corner of a m x n grid (marked 'Start' in the diagram below).The robot can only move either down or right at any point in time. The robot is trying to reach the

Follow up for "Unique Paths":Now consider if some obstacles are added to the grids. How many unique paths would there be?An obstacle and empty space is marked as 1 and 0 respectively in the

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

Validate if a given string is numeric.Some examples:"0" => true" 0.1 " => true"abc" => false"1 a" => false"2e10" => trueNote: It is intended for the problem statement to be ambiguo

Given a non-negative number represented as an array of digits, plus one to the number.The digits are stored such that the most significant digit is at the head of the list.这道题题意刚开始没看明白。。

Given a string s consists of upper/lower-case alphabets and empty space characters ' ', return the length of last word in the string.If the last word does not exist, return 0.Note: A word is

Given an absolute path for a file (Unix-style), simplify it.For example,path = "/home/", => "/home"path = "/a/./b/../../c/", => "/c"Corner Cases:Did you consider the case where path 

Given an array of strings, group anagrams together.For example, given: ["eat", "tea", "tan", "ate", "nat", "bat"], Return:[ ["ate", "eat","tea"], ["nat","tan"], ["bat"]]Note: Al

Implement pow(x, n).这道题最慢时间复杂度也是O(n)，快一些的是O（logn），主要是将n考虑为二进制的形式，某一位是1的话，就乘上相应的次方数即可。代码如下：public class Solution { public double myPow(double x, int n) { if(

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

Follow up for N-Queens problem.Now, instead outputting board configurations, return the total number of distinct solutions.这一题和上一题一样嘛。。代码几乎一模一样，就是返回原来的List的Size而已~代码如下：public cla

Find the contiguous subarray within an array (containing at least one number) which has the largest sum.For example, given the array [-2,1,-3,4,-1,2,1,-5,4],the contiguous subarray [4,-1,2,1] ha