#LeetCode: Power of Four

Also Check: August LeetCoding Challenge (2020)

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

Example 1:
Input: 16
Output: true

Example 2:
Input: 5
Output: false

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

Solution 1: With loop
In this approach we keep dividing the number by 4. If in any iteration n%4 becomes non-zero and n is not 1 then n is not a power of 4, otherwise n is a power of 4.

Solution 2: Without loop
If num & (0x55555555) != 0 then the answer is true, because if the number is a power of 2, there must be only one '1' bit and that '1' bit must be in the even position of the number.

FYI, for Hex number 0x55555555, the binary representation is 0101 0101 0101. The bit '1' must be in the even position. If the bit 1 (and the only bit 1) is in the odd position, the result of (num & 0x55555555) must be equal to zero.

GIT URL: Java Solution of Leet Code's Power of Four problem

Java Solution

ALSO CHECK: Other LeetCode Solutions in Java

-K Himaanshu Shuklaa.