[LeetCode 191] Number of 1 Bits

Write a function that takes an unsigned integer and returns the number of ’1' bits it has (also known as the Hamming weight).

For example, the 32-bit integer ’11' has binary representation 00000000000000000000000000001011, so the function should return 3.

solution:

1. every time n&1, until n==0. 

2. n&(n-1) will remove last 1 digit in n, use this to count how many 1 in the number

public int hammingWeight(int n) {
        int count = 0;
        while(n!=0){
            n = (n-1) & n;
            count++;
        }
        return count;
    }