191. Number of 1 Bits

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Problem

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

Note:

  Example 1:

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

Example 2:

Input: n = 00000000000000000000000010000000
Output: 1
Explanation: The input binary string 00000000000000000000000010000000 has a total of one '1' bit.

Example 3:

Input: n = 11111111111111111111111111111101
Output: 31
Explanation: The input binary string 11111111111111111111111111111101 has a total of thirty one '1' bits.

  Constraints:

  Follow up: If this function is called many times, how would you optimize it?

Solution

/**
 * @param {number} n - a positive integer
 * @return {number}
 */
var hammingWeight = function(n) {
    var count = 0;
    while (n) {
        if (n & 1) count++;
        n >>>= 1;
    }
    return count;
};

Explain:

use >>> instead of >>.

Complexity: