EchoChen1992-优快云博客

原创 [LeetCode] Divide Two Integers

题目Divide two integers without using multiplication, division and mod operator.If it is overflow, return MAX_INT.思路这道题需要用到移位操作，这就涉及到一些二进制相关的概念，先普及一下：1)二进制表示中，首位是符号位，1表示复数，0表示正数2)二进制表示

2016-01-05 10:08:05 350

原创 [LeetCode] Implement strStr()

题目Implement strStr().Returns the index of the first occurrence of needle in haystack, or -1 if needle is not part of haystack.思路按照下标递增的顺序比较haystack中的所有子字符串和needle。代码public class Solu

2016-01-05 10:04:09 282

原创 [LeetCode] Remove Element

题目Given an array and a value, remove all instances of that value in place and return the new length.The order of elements can be changed. It doesn't matter what you leave beyond the new length

2016-01-05 09:57:52 267

原创 [LeetCode] Remove Duplicates from Sorted Array

题目Given a sorted array, remove the duplicates in place such that each element appear only once and return the new length.Do not allocate extra space for another array, you must do this in pl

2016-01-04 20:18:52 248

原创 [LeetCode] Reverse Nodes in k-Group

题目Given a linked list, reverse the nodes of a linked list k at a time and return its modified list.If the number of nodes is not a multiple of k then left-out nodes in the end should remain

2016-01-04 20:12:49 264

原创 [LeetCode] Swap Nodes in Pairs

题目Given a linked list, swap every two adjacent nodes and return its head.For example,Given 1->2->3->4, you should return the list as 2->1->4->3.Your algorithm should use only constant

2016-01-04 20:05:00 251

原创 [LeetCode] Regular Expression Matching

题目Implement regular expression matching with support for '.' and '*'.'.' Matches any single character.'*' Matches zero or more of the preceding element.The matching should cover the entire

2016-01-04 19:57:05 262

原创 [LeetCode] Merge k Sorted Lists

题目Merge two sorted linked lists and return it as a new list. The new list should be made by splicing together the nodes of the first two lists.思路考察的是Two Pointers思想。开始这两个指针分别指向两个链表的头节点，每次取出这两

2016-01-04 19:47:28 234

原创 [LeetCode] Generate Parentheses

题目Given n pairs of parentheses, write a function to generate all combinations of well-formed parentheses.For example, given n = 3, a solution set is:"((()))", "(()())", "(())()", "()(())

2016-01-04 19:37:50 271

原创 [LeetCode] Merge Two Sorted Lists

题目Merge two sorted linked lists and return it as a new list. The new list should be made by splicing together the nodes of the first two lists.思路这道题比较简单，直接上代码。代码/** * Definition for sin

2015-12-08 16:37:06 323

原创 [LeetCode] Valid Parentheses

题目Given a string containing just the characters '(', ')', '{', '}', '[' and ']', determine if the input string is valid.The brackets must close in the correct order, "()" and "()[]{}" are

2015-12-08 16:29:49 253

原创 [LeetCode] Remove Nth Node From End of List

题目Given a linked list, remove the nth node from the end of list and return its head.For example, Given linked list: 1->2->3->4->5, and n = 2. After removing the second node from the

2015-12-08 16:24:03 380

原创 [Leetcode] 4Sum

题目Given anarray S of n integers, are thereelements a, b, c, and d in S suchthat a + b + c + d = target? Find allunique quadruplets in the array which gives the sum of target.Note:Elements in a

2015-12-08 16:21:43 291

原创 [LeetCode] Letter Combinations of a Phone Number

题目Given a digit string, return all possible letter combinations that the number could represent.A mapping of digit to letters (just like on the telephone buttons) is given below.Input:

2015-11-30 22:25:48 351

原创 [LeetCode] 3Sum Closest

题目Given an array S of n integers, find three integers in S such that the sum is closest to a given number, target. Return the sum of the three integers. You may assume that each input would have

2015-11-25 11:51:28 295

原创 [LeetCode] 3Sum

题目Given an array S of n integers, are there elements a, b, c in S such that a + b + c = 0? Find all unique triplets in the array which gives the sum of zero.Note:Elements in a triple

2015-11-20 15:38:15 298

原创 [LeetCode] Longest Common Prefix

题目Write a function to find the longest common prefix string among an array of strings.Subscribe to see which companies asked this question思路最长前缀，显然不可能比数组中任意一个字符串长。除去数组为空的特殊情况，选中第一个字符

2015-11-20 15:28:27 398

原创 [LeetCode] Roman to Integer

问题Given a roman numeral, convert it to an integer.Input is guaranteed to be within the range from 1 to 3999.Subscribe to see which companies asked this question思路罗马数字的构造方式上一篇博客里面

2015-11-20 14:55:34 273

原创 [LeetCode] Integer to Roman

题目Given an integer, convert it to a roman numeral.Input is guaranteed to be within the range from 1 to 3999.思路首先需要了解罗马数字的构造规律：罗马数字共有七个，即I(1)，V(5)，X(10)，L(50)，C(100)，D(500)，M(1000)。按照

2015-11-16 14:29:54 326

原创 [LeetCode] Container With Most Water

题目Given n non-negative integers a1, a2, ..., an, where each represents a point at coordinate (i, ai). n vertical lines are drawn such that the two endpoints of line i is at (i, ai) and (

2015-11-16 13:19:56 319

原创 [LeetCode] Palindrome Number

题目Determine whether an integer is a palindrome. Do this without extra space.click to show spoilers.Some hints:Could negative integers be palindromes? (ie, -1)If you are thinking of

2015-11-11 13:49:46 252

原创 [LeetCode] String to Integer (atoi)

题目Implement atoi to convert a string to an integer.Hint: Carefully consider all possible input cases. If you want a challenge, please do not see below and ask yourself what are the possible

2015-11-10 17:55:45 313

原创 [LeetCode] Reverse Integer

题目Reverse digits of an integer.Example1: x = 123, return 321Example2: x = -123, return -321click to show spoilers.Have you thought about this?Here are some good questions to ask

2015-11-10 16:28:42 407

原创 [LeetCode] ZigZag Conversion

题目The string "PAYPALISHIRING" is written in a zigzag pattern on a given number of rows like this: (you may want to display this pattern in a fixed font for better legibility)P A H NA

2015-11-10 15:14:24 463

原创 [LeetCode] Longest Palindromic Substring

题目Given a string S, find the longest palindromic substring in S. You may assume that the maximum length of S is 1000, and there exists one unique longest palindromic substring.思路1最直接的思

2015-11-09 20:44:31 273

原创 [LeetCode] Median of Two Sorted Arrays

题目There are two sorted arrays nums1 and nums2 of size m and n respectively. Find the median of the two sorted arrays. The overall run time complexity should be O(log (m+n)).思路题目中已经给出了时间复杂度的要

2015-11-04 15:25:05 381

原创 [LeetCode] Longest Substring Without Repeating Characters

题目：Given a string, find the length of the longest substring without repeating characters. For example, the longest substring without repeating letters for "abcabcbb" is "abc", which the length is

2015-11-04 12:26:27 343

原创 [LeetCode] Add Two Numbers

题目You are given two linked lists representing two non-negative numbers. The digits are stored in reverse order and each of their nodes contain a single digit. Add the two numbers and return it a

2015-11-03 17:04:00 373

原创 [LeetCode] Two Sum

题目Given an array of integers, find two numbers such that they add up to a specific target number.The function twoSum should return indices of the two numbers such that they add up to the t

2015-11-03 16:59:54 272

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