Today I have done leetcode's August LeetCoding Challenge with cpp.

August LeetCoding Challenge 22

Description

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.

Example 1:

Input: n = 16
Output: true

Example 2:

Input: n = 5
Output: false

Example 3:

Input: n = 1
Output: true

Constraints:

• -2^31 <= n <= 2^31 - 1

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

Solution

class Solution {
public:
  bool isPowerOfFour(int n) {
    return n && __builtin_popcount(n) == 1 && !(__builtin_ctz(n) & 1);
  }
};

// Accepted
// 1061/1061 cases passed (0 ms)
// Your runtime beats 100 % of cpp submissions
// Your memory usage beats 71.3 % of cpp submissions (5.8 MB)