LCM & GCD in TypeScript

lcm-and-gcd.ts

/**
 * LCM ... Least Common Multiple (最小公倍数)
 * GCD ... Greatest Common Divisor (最大公約数)
 *
 * LCM = (A * B) / GCD
 */

function _findGCD(a: number, b: number): number {
  if (a === 0) return b;
  if (b === 0) return a;

  return _findGCD(b, a % b);
}

export function findGCD(a: number, b: number): number {
  const [big, small] = a > b ? [a, b] : [b, a];
  return _findGCD(big, small);
}

export function findGCDs([first, ...rest]: number[]): number {
  if (first == null) return 0;

  return rest.reduce((acc, n) => findGCD(acc, n), first);
}

export function findLCM(a: number, b: number): number {
  if (a === 0 || b === 0) {
    return 0;
  }

  return a * b / findGCD(a, b);
}

export function findLCMs([first, ...rest]: number[]): number {
  if (first == null) return 0;

  return rest.reduce((acc, n) => findLCM(acc, n), first);
}