Power of Four
来源:互联网 发布:淘宝儿童丝袜模特 编辑:程序博客网 时间:2024/05/17 03:08
题目地址:https://leetcode.com/problems/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 loops/recursion?
判断一个数字是不是4的幂,首先,如果一个数字是4的幂的话,那么它肯定是2的幂,也就是说一个数字如果不是2的幂,那么它也就不是4的幂了。判断是否是2的幂,请参考Power of Two。
然后再看看这个数字与0x55555555的按位与的值是啥,为啥是0x55555555呢,先看看这个数字表示成二进制长啥样子:
1010101010101010101010101010101
就是奇数位都是1,偶数位都是0。如果这个数字与0x55555555按位与等于0的话,那么这个数就不是4的幂,否则是4的幂。
public class PowerofFour { public boolean isPowerOfFour(int num) { if (num <= 0) return false; if ((num & (num - 1)) != 0) return false; if ((num & 0x55555555) == 0) return false; return true; }}
0 0
- [LeetCode]Power of Four
- 342. Power of Four
- Power of Four-Leetcode
- LeetCode Power of Four
- LeetCode - Power of Four
- 113.Power of Four
- 342. Power of Four
- LeetCode342. Power of Four
- 342. Power of Four
- Power of Four
- leetcode_342 Power of Four
- LeetCode:Power of Four
- leetcode---Power of Four
- 342. Power of Four
- [LeetCode] Power of Four
- 342. Power of Four
- 342. Power of Four
- 【Leetcode】Power of Four
- 谷歌浏览器保存网页为mht插件
- 1072. Gas Station (30)
- Mac上安装mysql-mython报sh: mysql_config: command not found解决办法
- H5在canvas上截图
- hibernate检索策略
- Power of Four
- MVC模式
- 正则表达式
- JSP 学习内置对象:request response session。。。。。的常用方法
- [网络流24题-15] 汽车加油行驶 - 分层图
- 自定义ViewGroup实现流式布局
- 期货投资分析学习--考试
- 双绞线制作
- Hadoop API文档地址