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原创【LeetCode】94. Binary Tree Inorder Traversal

Given a binary tree, return the inorder traversal of its nodes' values.Example:Input: [1,null,2,3] 1 \ 2 / 3Output: [1,3,2]Follow up: Recursive solution is trivial, could y...

2018-08-30 10:47:11 152

原创【LeetCode】32. Longest Valid Parentheses

Given a string containing just the characters '(' and ')', find the length of the longest valid (well-formed) parentheses substring.Example 1:Input: "(()"Output: 2Explanation: The longest valid...

2018-08-21 11:56:29 226

原创【LeetCode】31. Next Permutation

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 o...

2018-08-12 06:40:22 191

原创【LeetCode】30. Substring with Concatenation of All Words

You are given a string, s, and a list of words, words, that are all of the same length. Find all starting indices of substring(s) in s that is a concatenation of each word in words exactly once and wi...

2018-08-11 04:33:37 281

原创【LeetCode】29. Divide Two Integers

Given two integers dividend and divisor, divide two integers without using multiplication, division and mod operator.Return the quotient after dividing dividend by divisor.The integer division sho...

2018-08-11 03:14:16 165

原创【LeetCode】28. Implement strStr()

Implement strStr().Return the index of the first occurrence of needle in haystack, or -1 if needle is not part of haystack.Example 1:Input: haystack = "hello", needle = "ll"Output: 2Example...

2018-08-10 11:41:13 153

原创【LeetCode】27. Remove Element

Given an array nums and a value val, remove all instances of that value in-place and return the new length.Do not allocate extra space for another array, you must do this by modifying the input arra...

2018-08-10 10:44:24 134

原创【LeetCode】26. Remove Duplicates from Sorted Array

Given a sorted array nums, 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 by modifyi...

2018-08-10 10:30:57 142

原创【LeetCode】25. Reverse Nodes in k-Group

Given a linked list, reverse the nodes of a linked list k at a time and return its modified list.k is a positive integer and is less than or equal to the length of the linked list. If the number of ...

2018-08-07 13:38:42 165

原创【LeetCode】24. Swap Nodes in Pairs

Example:Given 1->2->3->4, you should return the list as 2->1->4->3.Note:Your algorithm should use only constant extra space. You may not modify the values in the list's nodes...

2018-08-07 11:41:25 134

原创【LeetCode】23. Merge k Sorted Lists

Merge k sorted linked lists and return it as one sorted list. Analyze and describe its complexity.Example:Input:[ 1->4->5, 1->3->4, 2->6]Output: 1->1->2->3->4-...

2018-07-22 06:38:30 185

原创【LeetCode】22. Generate Parentheses

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:[ "((()))", "(()())", "(())()", "()(())", "...

2018-07-16 11:48:41 302

原创【LeetCode】21. Merge Two Sorted Lists

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.Example:Input: 1->2->4, 1->3->4Output: 1->1...

2018-07-15 00:32:59 189

原创【LeetCode】20. Valid Parentheses

Given a string containing just the characters '(', ')', '{', '}', '[' and ']', determine if the input string is valid.An input string is valid if:Open brackets must be closed by the same type of brack...

2018-07-15 00:02:18 184

原创【LeetCode】19. Remove Nth Node From End of List

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

2018-06-26 12:09:22 212

原创【LeetCode】18. 4Sum

Given 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 of tar...

2018-06-25 12:55:38 142

原创【LeetCode】17. Letter Combinations of a Phone Number

Given 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 like on the telephone buttons) is given...

2018-06-25 06:45:44 234

原创【LeetCode】16. 3Sum Closest

Given 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 input would ...

2018-06-20 10:42:01 162

原创【LeetCode】15. 3Sum

Given 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 contain ...

2018-06-20 09:53:29 135

原创【LeetCode】14. Longest Common Prefix

Write a function to find the longest common prefix string amongst an array of strings.If there is no common prefix, return an empty string "".Example 1:Input: ["flower","flow","flight"]Output: "fl"E...

2018-06-12 11:38:18 133

原创【LeetCode】13. Roman to Integer

Roman numerals are represented by seven different symbols: I, V, X, L, C, D and M.Symbol ValueI 1V 5X 10L 50C 100D 5...

2018-06-11 06:31:03 166

原创【LeetCode】12. Integer to Roman

Roman numerals are represented by seven different symbols: I, V, X, L, C, D and M.Symbol ValueI 1V 5X 10L 50C 100D 5...

2018-05-22 12:14:07 164

原创【LeetCode】11. Container With Most Water

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 (i, 0). Find two ...

2018-05-21 12:59:39 125

原创【LeetCode】10. Regular Expression Matching

Given an input string (s) and a pattern (p), implement regular expression matching with support for '.' and '*'.'.' Matches any single character.'*' Matches zero or more of the preceding element.The...

2018-05-15 12:09:03 188

原创【LeetCode】8. String to Integer (atoi)

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 input cases....

2018-04-10 03:09:06 173

原创【LeetCode】9. Palindrome Number

Determine whether an integer is a palindrome. Do this without extra space.思路：edge case:x < 0 ==> falsex == 0 ==> truex = 10, 100,... ==> false解法一：1. 如果input x是负数，直接返回false2. 考虑overflow情况，因...

2018-03-26 12:59:41 139

原创【LeetCode】7. Reverse Integer

Given a 32-bit signed integer, reverse digits of an integer.Example 1:Input: 123Output: 321Example 2:Input: -123Output: -321Example 3:Input: 120Output: 21Note:Assume we are dealing with an envi...

2018-03-26 11:26:57 139

原创【LeetCode】6. ZigZag Conversion

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 P L S I I G...

2018-03-26 10:16:33 121

原创【LeetCode】5. Longest Palindromic Substring

Given a string s, find the longest palindromic substring in s. You may assume that the maximum length of s is 1000.Example:Input: "babad"Output: "bab"Note: "aba" is also a valid answer. Example:I...

2018-03-26 06:19:02 145

原创【Leetcode】4. Median of Two Sorted Arrays

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)).Example 1:nums1 = [1, 3]nums2...

2018-03-25 11:55:36 139

原创【Leetcode】3. Longest Substring Without Repeating Characters

Given a string, find the length of the longest substring without repeating characters.Examples:Given "abcabcbb", the answer is "abc", which the length is 3.Given "bbbbb", the answer is "b", with the l...

2018-03-22 09:50:58 140

原创【Leetcode】2. Add Two Numbers

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

2018-03-22 08:36:45 196

原创【LeetCode】Search a 2D Matrix 解题报告

【题目】Write an efficient algorithm that searches for a value in an m x n matrix. This matrix has the following properties:Integers in each row are sorted from left to right.The first integer

2018-01-30 13:24:19 160

原创【LeetCode】Find Minimum in Rotated Sorted Array 解题报告

【题目】Suppose 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).Find the minimum element.You may

2018-01-29 12:12:46 159

原创【LeetCode】First Bad Version 解题报告

【题目】You are a product manager and currently leading a team to develop a new product. Unfortunately, the latest version of your product fails the quality check. Since each version is developed ba

2018-01-29 07:37:20 189

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