这三道题目都是一个意思,就是判断一个数是否为2/3/4的幂,这几道题里面有通用的方法,也有各自的方法,我会分别讨论讨论. 原题地址:231 Power of Two:https://leetcode.com/problems/power-of-two/description/ 326 Power of Three:https://leetcode.com/problems/power-of-three/description/ 342 Power of Four :https://leetcod…

231. Power of Two Given an integer, write a function to determine if it is a power of two. class Solution { public: bool isPowerOfTwo(int n) { ? (n & (n-)) == : false; } }; 342. Power of Four Given an integer (signed 32 bits), write a function to che…

这两题我放在一起说是因为思路一模一样,没什么值得研究的.思路都是用对数去判断. /** * @param {number} n * @return {boolean} */ var isPowerOfThree = function(n) { return (Math.log10(n) / Math.log10(3)) % 1 === 0; }; /** * @param {number} num * @return {boolean} */ var isPowerOfFour = functi…

1. 问题 231. Power of Two: 判断一个整数是否是2的n次方,其中n是非负整数 342. Power of Four: 判断一个整数是否是4的n次方,其中n是非负整数 326. Power of Three: 判断一个整数是否是3的n次方,其中n是非负整数 2. 思路 1)2的n次方  不妨列举几个满足条件的例子. If n = 0: 2 ^ n = 1 If n = 1: 2 ^ n = 2 -> 10(二进制表示) If n = 2: 2 ^ n = 4 -> 100(二…

leetcode 326. Power of Three(不用循环或递归) 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? 题意是判断一个数是否是3的幂,最简单的也最容易想到的办法就是递归判断,或者循环除. 有另一种方法就是,求log以3为底n的对数.类似 如果n=9,则…

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 loops/recursion? Credits:Special thanks to @yukuairoyfor…

342. Power of Four     Total Accepted: 707 Total Submissions: 2005 Difficulty: Easy 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:…

位运算相关 三道题 231. Power of Two Given an integer, write a function to determine if it is a power of two. (Easy) 分析: 数字相关题有的可以考虑用位运算,例如&可以作为筛选器. 比如n & (n - 1) 可以将n的最低位1删除,所以判断n是否为2的幂,即判断(n & (n - 1) == 0) 代码: class Solution { public: bool isPowerOf…

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POJ 1459 Power Network / HIT 1228 Power Network / UVAlive 2760 Power Network / ZOJ 1734 Power Network / FZU 1161 (网络流,最大流) Description A power network consists of nodes (power stations, consumers and dispatchers) connected by power transport lines. A…