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
O(1) time
Analysis:
Use bit manipulation. Be carefull about the 0 and negtive integer.
Solution:
1 class Solution { 2 /* 3 * @param n: An integer 4 * @return: True or false 5 */ 6 public boolean checkPowerOf2(int n) { 7 if (n<=0) return false; 8 boolean res = ((n & (n-1))==0) ? true : false; 9 return res; 10 } 11 };
LintCode-O(1) Check Power of 2
原文：http://www.cnblogs.com/lishiblog/p/4187964.html