Number of 1 Bits

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

Example 1:

Input: 00000000000000000000000000001011
Output: 3
Explanation: The input binary string 00000000000000000000000000001011 has a total of three '1' bits.

You may view the full question here.

Approach 1: Umm… Really not much to explain. The Leetcode Discussion forum has a plethora of information.

//Approach 1:
//Runtime: 1ms
//Memory usage: 32.4MB
public class Solution {
    // you need to treat n as an unsigned value
    public int hammingWeight(int n) {
        int count = 0;
        while(n!=0){
            if((n&1)==1){
                count++;
            }
            n = n>>>1;
        }
        return count;
    }
}

Approach 2: A little tweak —

//Approach 2:
//Runtime: 0ms
//Memory usage: 32.6MB
public class Solution {
    // you need to treat n as an unsigned value
    public int hammingWeight(int n) {
        int count = 0;
        while(n!=0){
            count += n&1;
            n = n>>>1;
        }
        return count;
    }
}

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Cheers & Chao!