Power of Two

Problem Statement - link #

Given an integer n, return true if it is a power of two. Otherwise, return false.

An integer n is a power of two, if there exists an integer x such that n == 2^x.

Examples #

Example 1:

Input: n = 1
Output: true
Explanation: 20 = 1

Example 2:

Input: n = 16
Output: true
Explanation: 24 = 16

Example 3:

Input: n = 3
Output: false

Example 4:

Input: n = 4
Output: true

Example 5:

Input: n = 5
Output: false

Constraints #

• -2^31 <= n <= 2^31 - 1

Follow up: Could you solve it without loops/recursion?

Solutions #

class Solution {
public:
    int one(int n){
        int c=0;
        for(unsigned int b = 1; b <= n && b > 0; b<<=1)
            if(n&b) c++;
        return c;
    }
    bool isPowerOfTwo(int n) {
        return n>0 ? one(n)==1 : false;
    }
};