Number of 1 Bits

• LeetCode: Number of 1 Bits

• Problem:

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.

• Analysis:

According to problems, the input is unsigned integer and want to get the Hamming weight.

Hamming weight is that the number of non-zero bit in a string.

• Code - Java:

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 < 32; i++) {
            count += (n >>> i) & 1;
        }
        return count;
    }
}

• Code - C++:

class Solution {
public:
    int hammingWeight(uint32_t n) {
        int count = 0;
        while (n > 0) {
            n &= (n - 1);
            count++;
        }
        return count;
    }
};

• Code - Python:

class Solution(object):
    def hammingWeight(self, n):
        """
        :type n: int
        :rtype: int
        """
        count = 0
        for i in range(32):
            count += (n >> i) & 1
        return count

• Code - C:

int hammingWeight(uint32_t n) {
    int count = 0;
    while (n > 0) {
        n &= (n - 1);
        count++;
    }
    return count;
}