Problem

Given an integer, write a function to determine if it is a power of two.

Example 1:

Input: 1

Output: true

Explanation: 20 = 1

Example 2:

Input: 16

Output: true

Explanation: 24 = 16

Example 3:

Input: 218

Output: false

Pre analysis

Will use the power of log2 .

Another solution

Recursive division

var isPowerOfTwo = function(n) {
    if(n === 0) {
        return false;
    }
    while(n % 2 === 0) {
        n = n / 2;
    }
    return n === 1;
};

Greedy solution

var isPowerOfTwo = function(n) {
    let exp = 0;
    let current = 1;

    while(current < n) {
        current = Math.pow(2, ++exp);
    }

    return current === n ? true : false;
};