Final Prices With a Special Discount in a Shop

export function finalPrices(prices: number[]): number[] {
  const answer = [...prices];
  const stack: number[] = [];
  prices.forEach((price, i) => {
    while (0 < stack.length && price <= prices[stack[stack.length - 1]]) {
      const prevIndex = stack.pop()!;
      answer[prevIndex] -= price;
    }
    stack.push(i);
  });
 
  return answer;
}