Count Set Bits in a Binary Number

easycodingAlgorithmsBit Manipulation~10 min

Asked at Google, Meta

Overview

Given a non-negative integer n, return the number of 1 bits in its binary representation (also known as the Hamming weight or popcount).

Constraints

0 <= n <= 2^31 - 1
Return a single integer.

Examples

hammingWeight(11);
// => 3
// Binary: 1011 has three 1-bits

hammingWeight(128);
// => 1
// Binary: 10000000

hammingWeight(0);
// => 0

Solution

Reveal solution

function hammingWeight(n) {
  let count = 0;
  while (n > 0) {
    count += n & 1;
    n = n >>> 1;
  }
  return count;
}

Each iteration checks the least significant bit and right-shifts. Using >>> 1 (unsigned right shift) avoids sign-extension issues.

Resources

count-set-bits.js

Count Set Bits in a Binary Number

easycodingAlgorithmsBit Manipulation

Overview

Given a non-negative integer n, return the number of 1 bits in its binary representation (also known as the Hamming weight or popcount).

Constraints

0 <= n <= 2^31 - 1
Return a single integer.

Examples

hammingWeight(11);
// => 3
// Binary: 1011 has three 1-bits

hammingWeight(128);
// => 1
// Binary: 10000000

hammingWeight(0);
// => 0

Solution

Reveal solution

function hammingWeight(n) {
  let count = 0;
  while (n > 0) {
    count += n & 1;
    n = n >>> 1;
  }
  return count;
}

Each iteration checks the least significant bit and right-shifts. Using >>> 1 (unsigned right shift) avoids sign-extension issues.

Resources

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