1701-average-waiting-time.js

/**
 * 1701. Average Waiting Time
 * https://leetcode.com/problems/average-waiting-time/
 * Difficulty: Medium
 *
 * There is a restaurant with a single chef. You are given an array customers, where
 * customers[i] = [arrivali, timei]:
 * - arrivali is the arrival time of the ith customer. The arrival times are sorted in
 *   non-decreasing order.
 * - timei is the time needed to prepare the order of the ith customer.
 *
 * When a customer arrives, he gives the chef his order, and the chef starts preparing it once
 * he is idle. The customer waits till the chef finishes preparing his order. The chef does not
 * prepare food for more than one customer at a time. The chef prepares food for customers in
 * the order they were given in the input.
 *
 * Return the average waiting time of all customers. Solutions within 10-5 from the actual
 * answer are considered accepted.
 */

/**
 * @param {number[][]} customers
 * @return {number}
 */
var averageWaitingTime = function(customers) {
  let totalWait = 0;
  let currentTime = 0;

  for (const [arrival, prepTime] of customers) {
    const startTime = Math.max(arrival, currentTime);
    const finishTime = startTime + prepTime;
    totalWait += finishTime - arrival;
    currentTime = finishTime;
  }

  return totalWait / customers.length;
};