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原创 Remove Element

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.c

2014-06-09 22:53:18 248

原创 Remove Duplicates from Sorted Array

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 place with

2014-06-05 11:06:20 299

原创 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.If the number of nodes is not a multiple of k then left-out nodes in the end should remain as it is

2014-06-03 17:43:13 410

原创 Merge k Sorted Lists

Merge k sorted linked lists and return it as one sorted list. Analyze and describe its complexity.class Solution {public: struct cmp{ bool operator()(ListNode* node1, ListNode* node2)

2014-05-31 23:21:32 336

原创 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:"((()))", "(()())", "(())()", "()(())", "()()

2014-05-28 17:46:34 447

原创 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 letters (just like on the telephone buttons) is given below.

2014-05-26 22:38:31 291

原创 4Sum

Given an array S of n integers, are there elements a, b, c, and d in S such that a + b + c + d = target? Find all unique quadruplets in the array which gives the sum of target.Note:Element

2014-05-22 22:38:08 310

原创 Longest Common Prefix

Write a function to find the longest common prefix string amongst an array of strings.class Solution {public: string longestCommonPrefix(vector &strs) { if (strs.size() == 0)

2014-05-21 13:04:48 232

原创 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). Fin

2014-05-19 21:24:54 323

原创 Regular Expression Matching

Implement regular expression matching with support for '.' and '*'.

2014-05-16 15:46:45 227

原创 3Sum Closest

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 exact

2014-05-14 20:28:45 369

原创 Roman to Integer

Given a roman numeral, convert it to an integer.Input is guaranteed to be within the range from 1 to 3999.class Solution {public: int romanToInt(string s) { mapmyMap; myMap['

2014-05-14 16:21:07 316

原创 Swap Nodes in Pairs

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 space. Y

2014-05-14 16:20:03 249

原创 Integer to Roman

Given an integer, convert it to a roman numeral.Input is guaranteed to be within the range from 1 to 3999.

2014-05-13 21:36:08 216

原创 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 ca

2014-05-09 16:20:35 249

原创 Median of Two Sorted Arrays

There are two sorted arrays A and B 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)).class Solution {public:

2014-05-08 22:43:25 246

原创 3Sum

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 triplet (a,b,c

2014-05-07 23:19:00 290

原创 Palindrome Number

Determine whether an integer is a palindrome. Do this without extra space.

2014-05-06 22:11:17 388

原创 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, and there exists one unique longest palindromic substring.O(n)

2014-05-05 22:53:00 245

原创 Validate Binary Search Tree

Given a binary tree, determine if it is a valid binary search tree (BST).Assume a BST is defined as follows:The left subtree of a node contains only nodes with keys less than the node's key.Th

2014-04-30 17:27:27 220

原创 Reverse Integer

Reverse digits of an integer.Example1: x = 123, return 321Example2: x = -123, return -321class Solution {public: int reverse(int x) { int result = 0; int flag = false;

2014-04-30 12:25:18 301

原创 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

2014-04-30 12:23:45 246

原创 Longest Substring Without Repeating Characters

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 3. Fo

2014-04-29 16:55:21 265

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 as a link

2014-04-29 13:45:43 278

原创 Valid Parentheses

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 all va

2014-04-28 16:32:21 301

原创 Pow(x, n)

class Solution {public: double pow(double x, int n) { double sum = 1.0; if(x == 0) { return 0; } else { if(n == 0

2014-04-28 13:11:37 284

原创 Same Tree

/** * Definition for binary tree * struct TreeNode { * int val; * TreeNode *left; * TreeNode *right; * TreeNode(int x) : val(x), left(NULL), right(NULL) {} * }; */cla

2014-04-28 10:07:36 247

原创 Two Sum

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 target, whe

2014-04-25 16:40:22 252

原创 Minimum Depth of Binary Tree

Given a binary tree, find its minimum depth.The minimum depth is the number of nodes along the shortest path from the root node down to the nearest leaf node.

2014-04-25 15:15:57 333

原创 Binary Tree Maximum Path Sum

Given a binary tree, find the maximum path sum.The path may start and end at any node in the tree.For example:Given the below binary tree, 1 / \ 2 3Return 6.

2014-04-25 14:34:57 537

原创 Remove Nth Node From End of List

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 end, the

2014-04-25 14:10:32 261

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