power_of_2.java

public class Solution {
    public boolean isPowerOfTwo(int n) {
        //return solutionOne(n);
        //return solutionTwo(n);
        return solutionThree(n);
    }
    
    private boolean solutionOne(int n) {
        // check the result of divition by 2 iteratively
        if(n == 0) return false;
        while(n != 1) {
            if(n%2 != 0) return false;
            n = n/2;
        }
        return true;
    }
     
    private boolean solutionTwo(int n) {
        if(n < 0) return false;
        int count = 0;
        while(n != 0) {
            if((n & 1) == 1) ++count;
            n = n>>1;
        }
        return count == 1 ? true : false;
    }
    
    private boolean solutionThree(int n) {
        if(n<0) return false;
        return Integer.bitCount(n) == 1 ? true:false;
    }
}