Power Of 2

Problem

Given a non-negative integer n. The task is to check if it is a power of 2.

Examples:

Example 1:

Input: n = 8
Output: true
Explanation: 8 is equal to 2 raised to 3 (2^3 = 8).

Example 2:

Input: n = 98
Output: false
Explanation: 98 cannot be obtained by any power of 2.

Example 3:

Input: n = 1
Output: true
Explanation: (2^0 = 1).

• Expected Time Complexity: $O(log n)$
• Expected Auxiliary Space: $O(1)$

Constraints:

$0 ≤ n < 10^{20}$

Solution

Python

def isPowerofTwo(self,n : int ) -> bool:
    if (n == 0):
        return False
    while (n != 1):
        if (n % 2 != 0):
            return False
        n = n // 2
    return True

Java

public static boolean isPowerofTwo(long n) {
    if (n == 0)
        return false;
    while (n != 1) {
        if (n % 2 != 0)
            return false;
        n = n / 2;
    }
    return true;
}

C

bool isPowerofTwo(long long n) {
    if (n == 0)
        return 0;
    while (n != 1) {
        if (n % 2 != 0)
            return 0;
        n = n / 2;
    }
    return 1;
}

C++

bool isPowerofTwo(long long n) {
    if (n == 0)
        return 0;
    while (n != 1) {
        if (n % 2 != 0)
            return 0;
        n = n / 2;
    }
    return 1;
}

• Time Complexity: $O(log n)$
• Auxiliary Space: $O(1)$