[LeetCode]--342. Power of Four (Bit Manipulation)

1. Problem

2. Loop Solution

First, give my loop solution! Very easy!

public class Solution { public boolean isPowerOfFour(int num) { if (num <= 0) return false; boolean res = true; while (num % 4 == 0) { num = num/4; } if (num != 1) res = false; return res; } }

3. Bit Manipulation

public class Solution { public boolean isPowerOfFour(int num) { return Integer.toBinaryString(num).matches("1(00)*"); } }

Besides, in jdk1.8, we can use the code below!

public boolean isPowerOfFour(int num) { return Integer.toString(num, 4).matches("10*"); }