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.
Example 2:
Input: 00000000000000000000000010000000
Output: 1
Explanation: The input binary string 00000000000000000000000010000000 has a total of one '1' bit.
Example 3:
Input: 11111111111111111111111111111101
Output: 31
Explanation: The input binary string 11111111111111111111111111111101 has a total of thirty one '1' bits.
- Change
n
to binary usingNumber.toString(2)
- Store in String using template literal
- Iterate & count 1
/**
* @param {number} n - a positive integer
* @return {number}
*/
var hammingWeight = function(n) {
let str = `${n.toString(2)}`
let count = 0
for (let i = 0; i < str.length; i++) {
if (str[i] == "1") count++
}
return count
}
- Rule of Thumb:
- Even number always ends with 0 & odd number always ends with 1
1 & 0 == 0
-> removes one
n & (n-1)
drops 1 each time
/**
* @param {number} n - a positive integer
* @return {number}
*/
var hammingWeight = function(n) {
let count = 0
while (n) {
n = n & (n - 1)
count++
}
return count
}
Reference Bits, Bytes, Building With Binary