Question

342. Power of Four

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Description

Given an integer n, return _true if it is a power of four. Otherwise, return false_.

An integer n is a power of four, if there exists an integer x such that n == 4x.

 

Example 1:

Input: n = 16
Output: true

Example 2:

Input: n = 5
Output: false

Example 3:

Input: n = 1
Output: true

 

Constraints:

• -231 <= n <= 231 - 1

 

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

Solutions

Solution 1

class Solution:
  def isPowerOfFour(self, n: int) -> bool:
    return n > 0 and (n & (n - 1)) == 0 and (n & 0xAAAAAAAA) == 0

class Solution {
  public boolean isPowerOfFour(int n) {
    return n > 0 && (n & (n - 1)) == 0 && (n & 0xaaaaaaaa) == 0;
  }
}

class Solution {
public:
  bool isPowerOfFour(int n) {
    return n > 0 && (n & (n - 1)) == 0 && (n & 0xaaaaaaaa) == 0;
  }
};

func isPowerOfFour(n int) bool {
  return n > 0 && (n&(n-1)) == 0 && (n&0xaaaaaaaa) == 0
}

function isPowerOfFour(n: number): boolean {
  return n > 0 && (n & (n - 1)) == 0 && (n & 0xaaaaaaaa) == 0;
}

/**
 * @param {number} n
 * @return {boolean}
 */
var isPowerOfFour = function (n) {
  return n > 0 && (n & (n - 1)) == 0 && (n & 0xaaaaaaaa) == 0;
};