[LeetCode 191] Number of 1 Bits

Question

link

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.

Credits:
Special thanks to @ts for adding this problem and creating all test cases.

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              <a class="btn btn-xs btn-primary" href="/tag/bit-manipulation/">Bit Manipulation</a>
              
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Analysis

In order to remove the last ‘1’ bit, we use this operation:

n = n & (n - 1);

Solution

Just remove all the ‘1’ bits.

Code

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