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原创 [Leetcode]Count Numbers with Unique Digits

Given a non-negative integer n, count all numbers with unique digits, x, where 0 ≤ x n.Example:Given n = 2, return 91. (The answer should be the total numbers in the range of 0 ≤ x < 100, excludin

2016-09-05 13:52:37 392

原创 [Leetcode]First Unique Character in a String

Given a string, find the first non-repeating character in it and return it's index. If it doesn't exist, return -1.Examples:s = "leetcode"return 0.s = "loveleetcode",return 2.Note: You may

2016-08-22 15:25:56 455

原创 [Leetcode]Ransom Note

Given  an  arbitrary  ransom  note  string  and  another  string  containing  letters from  all  the  magazines,  write  a  function  that  will  return  true  if  the  ransom  note  can  be  construc

2016-08-22 15:17:32 425

原创 [Leetcode]Power of Four

Given an integer (signed 32 bits), write a function to check whether it is a power of 4.Example:Given num = 16, return true.Given num = 5, return false.Follow up: Could you solve it without loop

2016-06-24 15:31:12 261

原创 [Leetcode]Reverse Vowels of a String

Write a function that takes a string as input and reverse only the vowels of a string.Example 1:Given s = "hello", return "holle".Example 2:Given s = "leetcode", return "leotcede".Subscrib

2016-06-23 15:04:16 188

原创 [Leetcode]Power of Three

Given an integer, write a function to determine if it is a power of three.Follow up:Could you do it without using any loop / recursion?Credits:Special thanks to @dietpepsi for adding this pr

2016-06-23 11:14:00 237

原创 [Leetcode]Intersection of Two Arrays II

Given two arrays, write a function to compute their intersection.Example:Given nums1 = [1, 2, 2, 1], nums2 = [2, 2], return[2, 2].Note:Each element in the result should appear as many ti

2016-06-21 12:23:53 317

原创 [Leetcode]Intersection of Two Arrays

Given two arrays, write a function to compute their intersection.Example:Given nums1 = [1, 2, 2, 1], nums2 = [2, 2], return[2].Note:Each element in the result must be unique.The result c

2016-06-20 18:37:36 223

原创 [Leetcode]Nim Game

You are playing the following Nim Game with your friend: There is a heap of stones on the table, each time one of you take turns to remove 1 to 3 stones. The one who removes the last stone will be the

2016-06-20 18:27:20 233

原创 [Leetcode]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#.

2016-03-15 18:51:00 298

原创 [Leetcode]Longest Increasing Path in a Matrix

Given an integer matrix, find the length of the longest increasing path.From each cell, you can either move to four directions: left, right, up or down. You may NOT move diagonally or move outside o

2016-03-14 14:49:11 317

原创 [Leetcode]Sudoku Solver

Write a program to solve a Sudoku puzzle by filling the empty cells.Empty cells are indicated by the character '.'.You may assume that there will be only one unique solution.A sudoku puzzle.

2016-03-10 19:42:23 263

原创 [Leetcode]Jump Game II

Given an array of non-negative integers, you are initially positioned at the first index of the array.Each element in the array represents your maximum jump length at that position.Your goal is

2016-03-09 22:40:57 315

原创 [Leetcode]Scramble String

Given a string s1, we may represent it as a binary tree by partitioning it to two non-empty substrings recursively.Below is one possible representation of s1 = "great": great / \ gr

2016-02-19 11:14:09 276

原创 [Leetcode]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], theref

2016-01-30 11:47:16 246

原创 [Leetcode]Insert Interval

Given a set of non-overlapping intervals, insert a new interval into the intervals (merge if necessary).You may assume that the intervals were initially sorted according to their start times.Examp

2016-01-29 16:14:55 311

原创 [Leetcode]Merge Intervals

Given a collection of intervals, merge all overlapping intervals.For example,Given [1,3],[2,6],[8,10],[15,18],return [1,6],[8,10],[15,18]./** * Definition for an interval. * struct Inter

2016-01-29 15:31:12 291

原创 [Leetcode]Remove Duplicate Letters

Given a string which contains only lowercase letters, remove duplicate letters so that every letter appear once and only once. You must make sure your result is the smallest in lexicographical order a

2016-01-29 12:15:19 411

原创 [Leetcode]Count of Smaller Numbers After Self

You are given an integer array nums and you have to return a new counts array. The counts array has the property where counts[i] is the number of smaller elements to the right of nums[i].Example:G

2016-01-20 18:08:32 1009

原创 [Leetcode]Edit Distance

Given two words word1 and word2, find the minimum number of steps required to convertword1 to word2. (each operation is counted as 1 step.)You have the following 3 operations permitted on a word:

2016-01-18 14:41:11 276

原创 [Leetcode]Odd Even Linked List

Given a singly linked list, group all odd nodes together followed by the even nodes. Please note here we are talking about the node number and not the value in the nodes.You should try to do it in p

2016-01-16 20:55:51 334

原创 [Leetcode]Remove Invalid Parentheses

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 ( and).

2016-01-14 20:14:43 318

原创 [Leetcode]Distinct Subsequences

Given a string S and a string T, count the number of distinct subsequences ofT in S.A subsequence of a string is a new string which is formed from the original string by deleting some (can be none

2016-01-08 10:43:05 278

原创 [Leetcode]Trapping Rain Water

Given n non-negative integers representing an elevation map where the width of each bar is 1, compute how much water it is able to trap after raining.For example, Given [0,1,0,2,1,0,1,3,2,1,2,1]

2016-01-05 10:19:10 279

原创 [Leetcode]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

2015-12-28 20:17:08 316

原创 [Leetcode]Longest Consecutive Sequence

Given an unsorted array of integers, find the length of the longest consecutive elements sequence.For example,Given [100, 4, 200, 1, 3, 2],The longest consecutive elements sequence is [1, 2, 3,

2015-12-17 20:06:59 409

原创 [Leetcode]N-Queens II

Follow up for N-Queens problem.Now, instead outputting board configurations, return the total number of distinct solutions.class Solution {public: /*algorithm: DFS */ vectorgetNex

2015-12-15 17:22:33 270

原创 [Leetcode]N-Queens

The n-queens puzzle is the problem of placing n queens on ann×n chessboard such that no two queens attack each other.Given an integer n, return all distinct solutions to the n-queens puzzle.Ea

2015-12-15 16:55:08 236

原创 [cc150]Chapter 3 | Stacks and Queues

Describe how you could use a single array to implement three stacks.1)solution 1 divide the array to 3 part, so each part can be one stack, but for each stack is limited to n/3 size [stk1][stk

2015-12-04 14:42:51 288

原创 [Leetcode]Binary Tree Postorder Traversal

Given a binary tree, return the postorder traversal of its nodes' values.For example:Given binary tree {1,#,2,3}, 1 \ 2 / 3return [3,2,1].Note: Recursive solution is tri

2015-12-03 18:10:20 225

原创 [Leetcode]Additive Number

Additive number is a string whose digits can form additive sequence.A valid additive sequence should contain at least three numbers. Except for the first two numbers, each subsequent number in the s

2015-12-02 23:22:40 562

原创 [Leetcode]Find the Duplicate Number

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

2015-12-01 15:37:38 239

原创 [Leetcode]Word Ladder

Given two words (beginWord and endWord), and a dictionary's word list, find the length of shortest transformation sequence frombeginWord to endWord, such that:Only one letter can be changed at a

2015-11-25 17:05:54 254

原创 [Leetcode]Range Sum Query - Immutable

Given an integer array nums, find the sum of the elements between indicesi and j (i ≤ j), inclusive.Example:Given nums = [-2, 0, 3, -5, 2, -1]sumRange(0, 2) -> 1sumRange(2, 5) -> -1sumRang

2015-11-23 15:11:08 207

原创 [Leetcode]Divide Two Integers

Divide two integers without using multiplication, division and mod operator.If it is overflow, return MAX_INT.class Solution {public: /*algorithm binary search */ int bSearch(lon

2015-11-19 15:11:26 233

原创 [Leetcode]Reverse Words in a String

Given an input string, reverse the string word by word.For example,Given s = "the sky is blue",return "blue is sky the".Update (2015-02-12):For C programmers: Try to solve it in-place in O(1

2015-11-18 00:08:17 244

原创 [Leetcode]Simplify Path

Given an absolute path for a file (Unix-style), simplify it.For example,path = "/home/", => "/home"path = "/a/./b/../../c/", => "/c"class Solution {public: /*algorithm for simplici

2015-11-14 22:06:12 238

原创 [Leetcode]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. For

2015-11-14 16:57:23 213

原创 [Leetcode]Range Sum Query 2D - Immutable

Given a 2D matrix matrix, find the sum of the elements inside the rectangle defined by its upper left corner (row1,col1) and lower right corner (row2, col2).The above rectangle (with the red bor

2015-11-14 16:11:38 234

原创 [Leetcode]Spiral Matrix

Given a matrix of m x n elements (m rows, n columns), return all elements of the matrix in spiral order.For example,Given the following matrix:[ [ 1, 2, 3 ], [ 4, 5, 6 ], [ 7, 8, 9 ]]You

2015-11-13 22:29:44 167

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