Using O(1) time to check whether an integer n is a power of 2.
For n=4, return true;
For n=5, return false;
奇数总是有超过2个1.
class Solution { /* * @param n: An integer * @return: True or false */ public boolean checkPowerOf2(int n) { if(n <= 0) return false; return (n & (n - 1)) == 0 ? true : false; } };
原文：http://www.cnblogs.com/beiyeqingteng/p/5697737.html