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.

思路

通过 n与n-1进行位与可以快速得到1的数量

Code

Java

public class Solution {
    // you need to treat n as an unsigned value
    public int hammingWeight(int n) {
        int sum=0;
        while(n != 0)
        {
            n&=n-1;
            sum++;
        }
        return sum;
    }
}