[LeetCode] Problem 342 - Power of Four

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

Example

No.1

Input: 16

Output: true

No.2

Input: 5

Output: false

Follow up

Could you solve it without loops/recursion?

Code

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public boolean isPowerOfFour(int num) {
    if (num <= 0)
        return false;
    
    // 1010101010101010101010101010101
    return (num & (num - 1)) == 0 && (num & 0x55555555) == num;
}