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原题链接https://leetcode.com/problems/number-complement/原题Given a positive integer, output its complement number. The complement strategy is to flip the bits of its binary representation.Note:The given int

原题链接https://leetcode.com/problems/hamming-distance/原题The Hamming distance between two integers is the number of positions at which the corresponding bits are different.Given two integers x and y, calcu

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 another

原题链接https://leetcode.com/problems/heaters/原题Winter is coming! Your first job during the contest is to design a standard heater with fixed warm radius to warm all the houses.Now, you are given positions

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 li

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 valid bu

Given an array containing n distinct numbers taken from 0, 1, 2, ..., n, find the one that is missing from the array.For example,Given nums = [0, 1, 3] return 2.Note:Your algorithm should run

Given a linked list, determine if it has a cycle in it. Follow up: Can you solve it without using extra space? 题目很明确，给定一个链表，判断其中是否包含一个环路。有个额外的要求就是不使用额外的空间。 假如说没有这个额外的要求，有什么方法可以解决呢？创建一个哈希表，遍历链表

很多人把在LeetCode上做题称之为刷题，对于已经掌握了相关算法的人来说，这样的称呼的确没有问题，但对于那些将LeetCode作为提高自己算法能力手段的人来说，“刷题”这个称呼并不算很合适。因为做题是一个提升自己能力的途径，如果只满足于把题目做完、状态变为accept的话，并不能最有效提高编程能力。 刚开始，我也犯了上面的错误，机械的做着上面的题目，只要通过了，就不再去想其他更巧妙的方法了。尤

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

原题题目要求常规解法更聪明的代码原题：You are playing the following Bulls and Cows game with your friend: You write down a number and ask your friend to guess what the number is. Each time your friend makes a guess,

原题题目要求解法原题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”. 题目要

原题题目要求解法原题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

原题Given two strings s and t which consist of only lowercase letters.String t is generated by random shuffling string s and then add one more letter at a random position.Find the letter that was added i

原题Find the sum of all left leaves in a given binary tree. Example: 3 / \ 9 20 / \ 15 7There are two left leaves in the binary tree, with values 9 and 15 respectively. Return 24.题

原题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 assume t

原题链接https://leetcode.com/problems/nth-digit/原题Find the nthn^th digit of the infinite integer sequence 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, …Note: n is positive and will fit within the range of a 32-bit

原题链接https://leetcode.com/problems/binary-watch/原题A binary watch has 4 LEDs on the top which represent the hours (0-11), and the 6 LEDs on the bottom represent the minutes (0-59).Each LED represents a z

原题链接https://leetcode.com/problems/add-strings/原题Given two non-negative numbers num1 and num2 represented as string, return the sum of num1 and num2.Note:The length of both num1 and num2 is < 5100.Both

原题链接https://leetcode.com/problems/convert-a-number-to-hexadecimal/原题Given an integer, write an algorithm to convert it to hexadecimal. For negative integer, two’s complement method is used.Note: 1. Al

原题链接https://leetcode.com/problems/longest-palindrome/原题Given a string which consists of lowercase or uppercase letters, find the length of the longest palindromes that can be built with those letters.T

原题链接https://leetcode.com/problems/rotate-function/原题Given an array of integers A and let n to be its length. Assume Bk to be an array obtained by rotating the array A k positions clock-wise, we define

原题链接https://leetcode.com/problems/assign-cookies/原题Assume you are an awesome parent and want to give your children some cookies. But, you should give each child at most one cookie. Each child i has a g