Power of Four

• LeetCode: Power of Four

• Problem:

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

• Follow up:

Could you solve it without loops/recursion?

• Examples:

Given num = 16, return true. Given num = 5, return false.

• Analysis:

num > 0 and (num & (num - 1) == 0) and ((num - 1) % 3 == 0)

• Code - Java:

class Solution {
    public boolean isPowerOfFour(int num) {
        int temp = num - 1;
        return num > 0 && (num & temp) == 0 && (temp) % 3 == 0;
    }
}

• Code - C++:

class Solution {
public:
    bool isPowerOfFour(int num) {
        int temp = num - 1;
        return num > 0 && (num & temp) == 0 && (temp) % 3 == 0;
    }
};

• Code - Python:

class Solution(object):
    def isPowerOfFour(self, num):
        """
        :type num: int
        :rtype: bool
        """
        temp = num - 1
        return num > 0 and (num & temp) == 0 and (temp % 3 == 0)

• Code - C:

bool isPowerOfFour(int num) {
    int temp = num - 1;
    return num > 0 && (num & temp) == 0 && (temp) % 3 == 0;
}