342. Power of Four

• Difficulty: Easy

• Topics: Bit Manipulation

• Similar Questions:

  • Power of Two

  • Power of Three

Problem:

Given an integer (signed 32 bits), write a function to check whether it is a power of 4.

Example 1:

Input: 16
Output: true

Input: 5
Output: false

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

Solutions:

class Solution {
public:
    bool isPowerOfFour(int num) {
        return num > 0 && ((num & (num - 1)) == 0) && ((num & 0x55555555) != 0);
    }
};