public class Solution {
public boolean isPowerOfFour(int num) {
return (num >= 0) && ((num & (num - 1)) == 0) && ((num - 1) % 3 == 0);
}
}
public class Solution {
public boolean isPowerOfFour(int num) {
if (num > 1) {
while (num % 4 == 0) num /= 4;
}
return num == 1;
}
}