Using O(1) time to check whether an integer n is a power of 2.
Example
For n=4, return true;
For n=5, return false;
Challenge
O(1) time
class Solution { /* * @param n: An integer * @return: True or false */ public boolean checkPowerOf2(int n) { // write your code here if (n<=0) return false; boolean res = ((n & (n-1))==0) ? true : false; return res; } };