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power of four

admin 11月 13, 2020 0

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

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

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

Credits:
Special thanks to @yukuairoy for adding this problem and creating all test cases.

Solution

class  {
    public boolean isPowerOfFour(int num) {
        if(num == 1) return true;
        if(num <= 3) return false;
        while(num > 1) {
            if((num&1) == 1) {
                return false;
            }
            num >>= 1;
            if((num&1) == 1) {
                return false;
            }
            num >>= 1;
        }
        return true;
    }
}