142. O(1) Check Power of 2【easy】

142. O(1) Check Power of 2【easy】

Using O(1) time to check whether an integer n is a power of 2.

Have you met this question in a real interview? 

Yes

Example

For n=4, return true;

For n=5, return false;

Challenge 

O(1) time

 

解法一：

class Solution {
public:
    /*
     * @param n: An integer
     * @return: True or false
     */
    bool checkPowerOf2(int n) {
        if (n > 0 && (n & n - 1) == 0) {
            return true;
        }
        
        return false;
    }
};