342. Power of Four

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

An integer n is a power of four, if there exists an integer x such that n == 4x.

class Solution {
    //4^0 + 4^1 + 4^2 .... + 4^15
    const int bit = 1431655765;
public:
    bool isPowerOfFour(int n) {
        if(n <= 0) return false;
        bitset<32> bi(n);
        return (bit & n) == n and bi.count() == 1;
    }
};