Algorithm
Problem Name: 342. Power of Four
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
Code Examples
#1 Code Example with C Programming
Code -
C Programming
bool isPowerOfFour(int num) {
// one bit only and has to be on 0101 0101 0101 0101
return num > 0 && (num&(num-1)) == 0 && (num & 0x55555555) != 0;
}
Input
n = 16
Output
true
#2 Code Example with Java Programming
Code -
Java Programming
class Solution {
public boolean isPowerOfFour(int n) {
long left = 0;
long right = n / 2 + 1;
while (left < = right) {
long mid = (left + right) / 2;
long pow = (long) (Math.pow(4, mid));
if (pow == ((long) n)) {
return true;
}
if (pow > ((long) n)) {
right = mid - 1;
} else {
left = mid + 1;
}
}
return false;
}
}
Input
n = 16
Output
true
#3 Code Example with Javascript Programming
Code -
Javascript Programming
const isPowerOfFour = function(num) {
if (num === 1) { return true; }
let f = 4;
while (f < = num) {
if (f === num) {
return true;
}
f *= 4;
}
return false;
};
Input
n = 5
Output
false
#4 Code Example with Python Programming
Code -
Python Programming
class Solution:
def isPowerOfFour(self, num: int) -> bool:
if num < 0:
return False
i = 1
while i < num:
i = i * 4
return i == num
Input
n = 5
Output
false
#5 Code Example with C# Programming
Code -
C# Programming
namespace LeetCode
{
public class _0342_PowerOfFour
{
public bool IsPowerOfFour(int num)
{
return num > 0 && ((num & (num - 1)) == 0) && ((num & 0xaaaaaaaa) == 0);
}
}
}
Input
n = 1
Output
true