Question

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

Example 1:

Input: 11
Output: 3
Explanation: Integer 11 has binary representation 00000000000000000000000000001011

Example 2:

Input: 128
Output: 1
Explanation: Integer 128 has binary representation 00000000000000000000000010000000

Thinking:

  • Method：
public class Solution {
    // you need to treat n as an unsigned value
    public int hammingWeight(int n) {
        int count = 0;
        for(int i = 0; i <= 31; i++){
            count = ((n & 1) == 1)? count + 1: count;
            n >>>= 1;
        }
        return count;
    }
}

二刷

public class Solution {
    // you need to treat n as an unsigned value
    public int hammingWeight(int n) {
        int count = 0;
        int cur = 1;
        for(int i = 0; i < 32; i++){
            if((n & (1 << i)) != 0)
                count ++;
        }
        return count;
    }
}