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原创 221. Maximal Square

Given a 2D binary matrix filled with 0's and 1's, find the largest square containing only 1's and return its area.For example, given the following matrix:1 0 1 0 01 0 1 1 11 1 1 1 11 0 0 1 0

2016-12-10 16:39:14 209

原创 146. LRU Cache

Design and implement a data structure for Least Recently Used (LRU) cache. It should support the following operations: get and set.get(key) - Get the value (will always be positive) of the key if

2016-12-09 14:04:33 242

原创 211. Add and Search Word - Data structure design

Design a data structure that supports the following two operations:void addWord(word)bool search(word)search(word) can search a literal word or a regular expression string containing only lett

2016-12-09 08:25:07 278

原创 208. Implement Trie (Prefix Tree)

Implement a trie with insert, search, and startsWith methods.Note:You may assume that all inputs are consist of lowercase letters a-z.class TrieNode { boolean isWord = false; // Stri

2016-12-09 08:23:32 190

原创 274,275. H-Index I, II

Given an array of citations (each citation is a non-negative integer) of a researcher, write a function to compute the researcher's h-index.According to the definition of h-index on Wikipedia: "A

2016-12-08 13:09:40 239

原创 257. Binary Tree Paths

Given a binary tree, return all root-to-leaf paths.For example, given the following binary tree: 1 / \2 3 \ 5All root-to-leaf paths are:["1->2->5", "1->3"]/**

2016-12-05 10:48:47 190

原创 297. Serialize and Deserialize Binary Tree

Serialization is the process of converting a data structure or object into a sequence of bits so that it can be stored in a file or memory buffer, or transmitted across a network connection link to be

2016-12-05 10:15:43 172

原创 10. Regular Expression Matching

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 input st

2016-12-05 07:58:50 311

原创 301. Remove Invalid Parentheses

题目：Remove the minimum number of invalid parentheses in order to make the input string valid. Return all possible results.Note: The input string may contain letters other than the parentheses

2016-12-05 04:46:37 199

原创 91. Decode Ways

A message containing letters from A-Z is being encoded to numbers using the following mapping:'A' -> 1'B' -> 2...'Z' -> 26Given an encoded message containing digits, determine the total nu

2016-12-05 03:04:28 221

原创 314. Binary Tree Vertical Order Traversal

题目：Given a binary tree, return the vertical order traversal of its nodes' values. (ie, from top to bottom, column by column).If two nodes are in the same row and column, the order should be fr

2016-12-04 08:59:10 232

原创 325. Maximum Size Subarray Sum Equals k

题目Given an array nums and a target value k, find the maximum length of a subarray that sums to k. If there isn't one, return 0 instead.Example 1:Given nums = [1, -1, 5, -2, 3], k = 3,return 4.

2016-12-04 08:45:51 232

原创 394. Decode String

Given an encoded string, return it's decoded string.The encoding rule is: k[encoded_string], where the encoded_string inside the square brackets is being repeated exactly k times. Note that k is

2016-11-17 02:28:29 191

原创 164. Maximum Gap

Given an unsorted array, find the maximum difference between the successive elements in its sorted form.Try to solve it in linear time/space.Return 0 if the array contains less than 2 elements

2016-11-13 05:00:17 242

原创 373. Find K Pairs with Smallest Sums

You are given two integer arrays nums1 and nums2 sorted in ascending order and an integer k.Define a pair (u,v) which consists of one element from the first array and one element from the second a

2016-11-08 09:00:24 177

原创 Heap & Priority Queue

Heap: array implementationint[] heap, int heapSize = 0;parent and children: parent(i)=i/2; children(i) = {ix2, ix2+1}insert(int a): bubble-up private static void insert(int a, int[] h

2016-11-08 08:47:53 336

原创 374,375. Guess Number Higher or Lower I,II

We are playing the Guess Game. The game is as follows:I pick a number from 1 to n. You have to guess which number I picked.Every time you guess wrong, I'll tell you whether the number I pi

2016-11-03 14:22:42 283

原创 32. Longest Valid Parentheses

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 "()",

2016-11-03 01:07:03 187

原创 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

2016-11-02 16:19:50 222

原创 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

2016-11-01 15:15:46 177

原创 287. Find the Duplicate Number

Given an array nums containing n + 1 integers where each integer is between 1 and n (inclusive), prove that at least one duplicate number must exist. Assume that there is only one duplicate number,

2016-11-01 01:18:37 167

原创 371. Sum of Two Integers

Calculate the sum of two integers a and b, but you are not allowed to use the operator + and -.Example:Given a = 1 and b = 2, return 3.思路：a^b异或等于无进位的加法，(a&b)解法一：public class Solution {

2016-11-01 00:15:57 161

原创 223. Rectangle Area

Find the total area covered by two rectilinear rectangles in a 2D plane.Each rectangle is defined by its bottom left corner and top right corner as shown in the figure.Assume that the tota

2016-10-27 07:48:56 181

原创 217, 219,220. Contains Duplicate I, II, III

Given an array of integers, find if the array contains any duplicates. Your function should return true if any value appears at least twice in the array, and it should return false if every element

2016-10-27 01:40:41 296

原创 209. Minimum Size Subarray Sum

Given an array of n positive integers and a positive integer s, find the minimal length of a subarray of which the sum ≥ s. If there isn't one, return 0 instead.For example, given the array [2,3

2016-10-22 02:25:28 177

原创 207,210. Course Schedule I, II

There are a total of n courses you have to take, labeled from 0 to n - 1.Some courses may have prerequisites, for example to take course 0 you have to first take course 1, which is expressed as

2016-10-21 16:16:21 280

原创 206. Reverse Linked List

Reverse a singly linked list./** * Definition for singly-linked list. * public class ListNode { * int val; * ListNode next; * ListNode(int x) { val = x; } * } */public class Solu

2016-10-21 15:35:17 139

原创 205. Isomorphic Strings

Given two strings s and t, determine if they are isomorphic.Two strings are isomorphic if the characters in s can be replaced to get t.All occurrences of a character must be replaced with anot

2016-10-21 09:13:03 160

原创 204. Count Primes

Description:Count the number of prime numbers less than a non-negative number, n.思路：从前向后扫描，第一次遇到没标记的应该是没有因子的质数。然后把后面所有这个质数的倍数都标记了。 public int countPrimes(int n) { if(n<2) retur

2016-10-21 08:54:44 154

原创 203. Remove Linked List Elements

Remove all elements from a linked list of integers that have value val.ExampleGiven: 1 --> 2 --> 6 --> 3 --> 4 --> 5 --> 6, val = 6Return: 1 --> 2 --> 3 --> 4 --> 5/** * Definition for si

2016-10-20 07:27:44 185

原创 202. Happy Number

Write an algorithm to determine if a number is "happy".A happy number is a number defined by the following process: Starting with any positive integer, replace the number by the sum of the squares

2016-10-20 07:23:00 195

原创 201. Bitwise AND of Numbers Range

Given a range [m, n] where 0 For example, given the range [5, 7], you should return 4.思路：从左到右比较m和n的二进制数，相同的base加起来，直到出现不同的base，停止比较，因为后面一定是0，1交错的，而前面的一定是相同的（比较过来的），只要返回这些相同部分。public class

2016-10-20 06:59:38 174

原创 200. Number of Islands

Given a 2d grid map of '1's (land) and '0's (water), count the number of islands. An island is surrounded by water and is formed by connecting adjacent lands horizontally or vertically. You may assu

2016-10-20 05:25:37 166

原创 198. House Robber

You are a professional robber planning to rob houses along a street. Each house has a certain amount of money stashed, the only constraint stopping you from robbing each of them is that adjacent house

2016-10-20 04:59:55 184

原创 191. Number of 1 Bits

Write a function that takes an unsigned integer and returns the number of ’1' bits it has (also known as the Hamming weight).For example, the 32-bit integer ’11' has binary representation 000000

2016-10-20 02:37:21 165

原创 121.122.123.188. Best Time to Buy and Sell Stock I II III IV

Say you have an array for which the ith element is the price of a given stock on day i.If you were only permitted to complete at most one transaction (ie, buy one and sell one share of the stock),

2016-10-18 08:23:58 300

原创 283. Move Zeroes

Given an array nums, write a function to move all 0's to the end of it while maintaining the relative order of the non-zero elements.For example, given nums = [0, 1, 0, 3, 12], after calling you

2016-10-18 07:48:28 147

原创 190. Reverse Bits

Reverse bits of a given 32 bits unsigned integer.For example, given input 43261596 (represented in binary as 00000010100101000001111010011100), return 964176192 (represented in binary as 001110010

2016-10-18 02:28:22 264

原创 189. Rotate Array

Rotate an array of n elements to the right by k steps.For example, with n = 7 and k = 3, the array [1,2,3,4,5,6,7] is rotated to [5,6,7,1,2,3,4].Try to come up as many solutions as you can,

2016-10-14 09:11:08 178

原创 187. Repeated DNA Sequences

All DNA is composed of a series of nucleotides abbreviated as A, C, G, and T, for example: "ACGAATTCCG". When studying DNA, it is sometimes useful to identify repeated sequences within the DNA.Wri

2016-10-12 07:26:07 145

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