Number of 1 Bits

Problem (restated)

Return the number of set bits (Hamming weight) in a 32-bit integer.

Intuition

n &= n-1 clears the lowest set bit; count until n=0.

Approaches

export function hammingWeight(n: number): number {
  let c = 0;
  n >>>= 0;
  while (n) {
    n &= n - 1;
    c++;
  }
  return c;
}

export function hammingWeight(n: number): number {
  let c = 0;
  n >>>= 0;
  while (n) {
    n &= n - 1;
    c++;
  }
  return c;
}

Template connection

Bit manipulation set-bit checks.

Reflection

• Which pattern gave this away within 90 seconds?
• What changed from the standard template?
• What would break the current solution?