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Determine whether an integer is a palindrome. Do this without extra space.public class Solution {    public boolean isPalindrome(int x) {        String s=Integer.toString(x);        char[] a=s

Given two strings s and t, write a function to determine if t is an anagram of s.For example,s = "anagram", t = "nagaram", return true.s = "rat", t = "car", return false.Note:You may assum

Given a binary tree, find its maximum depth.The maximum depth is the number of nodes along the longest path from the root node down to the farthest leaf node.因为有前边的一些练习，这道题目做起来简直是太简单。主要思路：用一

Reverse digits of an integer.Example1: x = 123, return 321Example2: x = -123, return -321对于这道题目，如果超出整数限制，那么返回0public class Solution {    public int reverse(int x) {        int a=Math

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"]转载出处http://se

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

Given a binary tree, return the bottom-up level order traversal of its nodes' values. (ie, from left to right, level by level from leaf to root).For example:Given binary tree {3,9,20,#,#,15,7},

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.转载出处：http://www.cn

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)).public class Solution {

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

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

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, where

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

转载出处   http://blog.youkuaiyun.com/xudli/article/details/46838747Given a binary search tree (BST), find the lowest common ancestor (LCA) of two given nodes in the BST.According to the definition of

Given a binary tree, return the level order traversal of its nodes' values. (ie, from left to right, level by level).For example:Given binary tree {3,9,20,#,#,15,7}, 3 / \ 9 20 /

Invert a binary tree. 4 / \ 2 7 / \ / \1 3 6 9to 4 / \ 7 2 / \ / \9 6 3 1/**  * Definition for a binary tree node.  * public class TreeNod

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

Given an array of integers and an integer k, find out whether there are two distinct indicesi and j in the array such that nums[i] = nums[j] and the difference betweeni and j is at most k.出处：htt

出处http://www.thinksaas.cn/group/topic/395502/Find the total area covered by two rectilinear rectangles in a2D plane.Each rectangle is defined by its bottom left corner and top right corner a

Implement the following operations of a stack using queues.push(x) -- Push element x onto stack.pop() -- Removes the element on top of the stack.top() -- Get the top element.empty() -- Return whet

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

出处：http://blog.youkuaiyun.com/xudli/article/details/46645087Given a sorted integer array without duplicates, return the summary of its ranges.For example, given [0,1,2,4,5,7], return ["0->2","4->5",

Given an integer, write a function to determine if it is a power of two.public class Solution {     public boolean isPowerOfTwo(int n) {         if(n==0)             return false;

Implement the following operations of a queue using stacks.push(x) -- Push element x to the back of queue.pop() -- Removes the element from in front of queue.peek() -- Get the front element.empty(

Given two sorted integer arrays nums1 and nums2, merge nums2 intonums1 as one sorted array.Note:You may assume that nums1 has enough space (size that is greater or equal tom + n) to hold addit

Given two binary trees, write a function to check if they are equal or not.Two binary trees are considered equal if they are structurally identical and the nodes have the same value./**  * Defin

Given a binary tree, check whether it is a mirror of itself (ie, symmetric around its center).For example, this binary tree is symmetric: 1 / \ 2 2 / \ / \3 4 4 3But the following

Given a pattern and a string str, find if str follows the same pattern.Here follow means a full match, such that there is a bijection between a letter inpattern and a non-empty word in str.Examp

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 your fu

Given a binary tree, determine if it is height-balanced.For this problem, a height-balanced binary tree is defined as a binary tree in which the depth of the two subtrees ofevery node never differ

Compare two version numbers version1 and version2.If version1 > version2 return 1, if version1 version2 return -1, otherwise return 0.You may assume that the version strings are non-empty and co

Given an array of size n, find the majority element. The majority element is the element that appears more than⌊ n/2 ⌋ times.You may assume that the array is non-empty and the majority element alw

Related to question Excel Sheet Column TitleGiven a column title as appear in an Excel sheet, return its corresponding column number.For example: A -> 1 B -> 2 C -> 3 ... Z

Given an integer n, return the number of trailing zeroes in n!.Note: Your solution should be in logarithmic time complexity.//含因子5为几个就是几个0，像25*4=100，所以25含有2个5，http://www.zhihu.com/question/3

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]. Note:Try to come up as many solutions as you ca

Given a singly linked list, determine if it is a palindrome.Follow up:Could you do it in O(n) time and O(1) space?public class Solution {     public boolean isPalindrome(ListNode head) {

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

Reverse bits of a given 32 bits unsigned integer.For example, given input 43261596 (represented in binary as 00000010100101000001111010011100), return 964176192 (represented in binary as0011100101

Write a function that takes an unsigned integer and returns the number of ’1' bits it has (also known as theHamming weight).For example, the 32-bit integer ’11' has binary representation 000000000

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