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原创 75. Sort Colors

Given an array with n objects colored red, white or blue, sort them so that objects of the same color are adjacent, with the colors in the order red, white and blue.Here, we will use the integers

2017-06-22 08:59:15 251

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].用三个反转，空间复杂度为O(1)public class Solution {

2017-06-04 11:43:54 227

原创 581. Shortest Unsorted Continuous Subarray

Given an integer array, you need to find one continuous subarray that if you only sort this subarray in ascending order, then the whole array will be sorted in ascending order, too.You need to fin

2017-06-02 15:54:07 383

原创 95. Unique Binary Search Trees II

Given an integer n, generate all structurally unique BST's (binary search trees) that store values 1...n.For example,Given n = 3, your program should return all 5 unique BST's shown below. 1

2017-04-25 22:05:35 303

原创 494. Target Sum

You are given a list of non-negative integers, a1, a2, ..., an, and a target, S. Now you have 2 symbols + and -. For each integer, you should choose one from + and - as its new symbol.Find out

2017-04-25 17:04:50 322

原创 542. 01 Matrix

Given a matrix consists of 0 and 1, find the distance of the nearest 0 for each cell.The distance between two adjacent cells is 1.Example 1: Input:0 0 00 1 00 0 0Output:0 0 00 1 00

2017-03-19 11:11:04 402

原创 399. Evaluate Division

Equations are given in the format A / B = k, where A and B are variables represented as strings, and k is a real number (floating point number). Given some queries, return the answers. If the answ

2017-03-03 14:58:36 230

原创实习编程题

大意：给一个整数数组，从中去掉3个数从而将数组分为4个子数组，使得这4个子数组的和相同。判断是否存在这样的3个数。一开始拿到题目的时候，连题目都理解错了。30分钟时间太短了。使用3个指针，分别指想第1，2，3个数。然后移动两边的指针，使得第一部分和第4部分的和相同，然后移动第二个指针，在第二部分小于第一部分时，第二个指针向右移。public class Solution {

2017-03-02 13:18:51 263

原创 274. H-Index

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

2017-02-28 16:59:17 243

Remember the story of Little Match Girl? By now, you know exactly what matchsticks the little match girl has, please find out a way you can make one square by using up all those matchsticks. You shoul

2017-02-28 16:23:53 299

原创 114. Flatten Binary Tree to Linked List

Given a binary tree, flatten it to a linked list in-place.For example,Given 1 / \ 2 5 / \ \ 3 4 6The flattened tree should look like: 1

2017-02-28 14:35:44 211

原创 524. Longest Word in Dictionary through Deleting

Given a string and a string dictionary, find the longest string in the dictionary that can be formed by deleting some characters of the given string. If there are more than one possible results, retur

2017-02-28 11:03:15 309

原创 90. Subsets II

Given a collection of integers that might contain duplicates, nums, return all possible subsets.Note: The solution set must not contain duplicate subsets.For example,If nums = [1,2,2], a sol

2017-02-28 09:37:21 230

原创 376. Wiggle Subsequence

A sequence of numbers is called a wiggle sequence if the differences between successive numbers strictly alternate between positive and negative. The first difference (if one exists) may be either pos

2017-02-27 15:13:10 288

原创 80. Remove Duplicates from Sorted Array II

Follow up for "Remove Duplicates":What if duplicates are allowed at most twice?For example,Given sorted array nums = [1,1,1,2,2,3],Your function should return length = 5, with the first fi

2017-02-27 11:29:47 227

原创 450. Delete Node in a BST

Given a root node reference of a BST and a key, delete the node with the given key in the BST. Return the root node reference (possibly updated) of the BST.Basically, the deletion can be divided i

2017-02-26 15:54:21 245

原创 73. Set Matrix Zeroes

Given a m x n matrix, if an element is 0, set its entire row and column to 0. Do it in place.如果空间复杂度为O(m+n)，那十分的简单。在要求O（1）的情况下，我们需要使用数组本身来记录0的位置。思考过程：使用m+n个数来分别记录需要清零的行和列，相当于在数组外额外增加一行和一列。所以

2017-02-26 14:20:14 371

原创 375. Guess Number Higher or Lower 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

2017-02-25 18:37:19 214

原创 331. Verify Preorder Serialization of a Binary Tree

One way to serialize a binary tree is to use pre-order traversal. When we encounter a non-null node, we record the node's value. If it is a null node, we record using a sentinel value such as #.

2017-02-25 15:05:17 199

原创 129. Sum Root to Leaf Numbers

Given a binary tree containing digits from 0-9 only, each root-to-leaf path could represent a number.An example is the root-to-leaf path 1->2->3 which represents the number 123.Find the tota

2017-02-25 11:15:23 259

原创 395. Longest Substring with At Least K Repeating Characters

Find the length of the longest substring T of a given string (consists of lowercase letters only) such that every character in T appears no less than k times.Example 1:Input:s = "aaabb", k =

2017-02-25 10:36:31 184

原创 279. Perfect Squares

Given a positive integer n, find the least number of perfect square numbers (for example, 1, 4, 9, 16, ...) which sum to n.For example, given n = 12, return 3 because 12 = 4 + 4 + 4; given

2017-02-24 18:04:16 192

原创 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,

2017-02-24 11:22:17 169

原创 39. Combination Sum

Given a set of candidate numbers (C) (without duplicates) and a target number (T), find all unique combinations in C where the candidate numbers sums to T.The same repeated number may be

2017-02-23 17:01:35 187

原创 289. Game of Life

According to the Wikipedia's article: "The Game of Life, also known simply as Life, is a cellular automaton devised by the British mathematician John Horton Conway in 1970."Given a board with m

2017-02-23 16:45:49 205

原创 116. Populating Next Right Pointers in Each Node

Given a binary tree struct TreeLinkNode { TreeLinkNode *left; TreeLinkNode *right; TreeLinkNode *next; }Populate each next pointer to point to its next right node.

2017-02-23 15:42:41 189

原创 474. Ones and Zeroes

In the computer world, use restricted resource you have to generate maximum benefit is what we always want to pursue.For now, suppose you are a dominator of m 0s and n 1s respectively. On the ot

2017-02-23 15:01:45 191

原创 313. Super Ugly Number

Write a program to find the nth super ugly number.Super ugly numbers are positive numbers whose all prime factors are in the given prime list primes of size k. For example, [1, 2, 4, 7, 8, 13,

2017-02-22 15:01:46 204

原创 48. Rotate Image

You are given an n x n 2D matrix representing an image.Rotate the image by 90 degrees (clockwise).创建一个数组，直接把元素放到合适的位置。public class Solution { public void rotate(int[][] matrix) { i

2017-02-22 09:50:31 189

原创 64. Minimum Path Sum

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.非常简单的动态规划问题public class Solution { pu

2017-02-21 20:41:23 172

原创 215. Kth Largest Element in an Array

Find the kth largest element in an unsorted array. Note that it is the kth largest element in the sorted order, not the kth distinct element.For example,Given [3,2,1,5,6,4] and k = 2, return 5.

2017-02-21 16:59:08 205

原创 240. Search a 2D Matrix II +74. Search a 2D Matrix

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 in ascending from left to right.Integers in

2017-02-21 11:23:16 186

原创 78. Subsets

Given a set of distinct integers, nums, return all possible subsets.Note: The solution set must not contain duplicate subsets.For example,If nums = [1,2,3], a solution is:[ [3], [1],

2017-02-20 21:52:28 187

原创 416. Partition Equal Subset Sum

Given a non-empty array containing only positive integers, find if the array can be partitioned into two subsets such that the sum of elements in both subsets is equal.Note:Each of the array

2017-02-20 21:18:02 184

原创 40. Combination Sum II

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

2017-02-20 20:24:13 172

原创 300. Longest Increasing Subsequence

Given an unsorted array of integers, find the length of longest increasing subsequence.For example,Given [10, 9, 2, 5, 3, 7, 101, 18],The longest increasing subsequence is [2, 3, 7, 101], ther

2017-02-20 14:57:29 188

原创 334. Increasing Triplet Subsequence

Given an unsorted array return whether an increasing subsequence of length 3 exists or not in the array.Formally the function should:Return true if there exists i, j, k such that arr[i] ar

2017-02-20 10:40:02 160

原创 77. Combinations

Given two integers n and k, return all possible combinations of k numbers out of 1 ... n.For example,If n = 4 and k = 2, a solution is:[ [2,4], [3,4], [2,3], [1,2], [1,3], [1,4],]

2017-02-19 14:17:24 266

原创 380. Insert Delete GetRandom O(1)

Design a data structure that supports all following operations in average O(1) time.insert(val): Inserts an item val to the set if not already present.remove(val): Removes an item val from the

2017-02-18 22:15:12 217

原创 153. Find Minimum in Rotated Sorted Array

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 assume no

2017-02-18 16:33:42 176

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