Power of Four Problem & Solution
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 == 4^x.
See the power of four problem on LeetCode.
C++ Solution
#pragma GCC optimize("Ofast")
static const int _=[](){std::ios::sync_with_stdio(false);cin.tie(nullptr);cout.tie(nullptr);return 0;}();
class Solution {
public:
bool isPowerOfFour(int n) {
// To be a power of 4, the number must:
// 1. Have only one 1 in its binary representation.
// 2. The number of trailing zeroes must be divisible by 2.
return __builtin_popcount(n) == 1 && __builtin_ctz(n) % 2 == 0;
}
};