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LeetCode Problem 1701: Average Waiting Time - Step-by-Step Solutions

Problem Description

Given an array customers where customers[i] = [arrivali, timei]:

  • arrivali is the arrival time of the ith customer.
  • timei is the time needed to prepare the order of the ith customer.

The chef starts preparing the order as soon as the previous order is finished. The goal is to calculate the average waiting time for all customers.

C++ Solution

Step-by-Step Explanation

  1. Initialize Variables:

    • total_waiting_time to accumulate the total waiting time.
    • current_time to track when the chef is available to start the next order.
    long long total_waiting_time = 0;
int current_time = 0;

  2. Iterate Through Each Customer:

    • Extract arrival_time and cooking_time for each customer.
    • Update current_time to the maximum of the current time or the customer's arrival time plus the cooking time.
    • Calculate the waiting time for the current customer and add it to total_waiting_time.
    for (const auto& customer : customers) {
    int arrival_time = customer[0];
    int cooking_time = customer[1];
    
    current_time = max(current_time, arrival_time) + cooking_time;
    total_waiting_time += current_time - arrival_time;
}

  3. Calculate and Return Average Waiting Time:

    • Divide total_waiting_time by the number of customers to get the average waiting time.
    return (double)total_waiting_time / customers.size();

Complete Code

class Solution {
public:
    double averageWaitingTime(vector<vector<int>>& customers) {
        long long total_waiting_time = 0;
        int current_time = 0;
        
        for (const auto& customer : customers) {
            int arrival_time = customer[0];
            int cooking_time = customer[1];
            
            current_time = max(current_time, arrival_time) + cooking_time;
            total_waiting_time += current_time - arrival_time;
        }
        
        return (double)total_waiting_time / customers.size();
    }
};

Java Solution

Step-by-Step Explanation

  1. Initialize Variables:

    • totalWaitingTime to accumulate the total waiting time.
    • currentTime to track when the chef is available to start the next order.
    long totalWaitingTime = 0;
int currentTime = 0;

  2. Iterate Through Each Customer:

    • Extract arrivalTime and cookingTime for each customer.
    • Update currentTime to the maximum of the current time or the customer's arrival time plus the cooking time.
    • Calculate the waiting time for the current customer and add it to totalWaitingTime.
    for (int[] customer : customers) {
    int arrivalTime = customer[0];
    int cookingTime = customer[1];
    
    currentTime = Math.max(currentTime, arrivalTime) + cookingTime;
    totalWaitingTime += currentTime - arrivalTime;
}

  3. Calculate and Return Average Waiting Time:

    • Divide totalWaitingTime by the number of customers to get the average waiting time.
    return (double) totalWaitingTime / customers.length;

Complete Code

class Solution {
    public double averageWaitingTime(int[][] customers) {
        long totalWaitingTime = 0;
        int currentTime = 0;
        
        for (int[] customer : customers) {
            int arrivalTime = customer[0];
            int cookingTime = customer[1];
            
            currentTime = Math.max(currentTime, arrivalTime) + cookingTime;
            totalWaitingTime += currentTime - arrivalTime;
        }
        
        return (double) totalWaitingTime / customers.length;
    }
}

JavaScript Solution

Step-by-Step Explanation

  1. Initialize Variables:

    • totalWaitingTime to accumulate the total waiting time.
    • currentTime to track when the chef is available to start the next order.
    let totalWaitingTime = 0;
let currentTime = 0;

  2. Iterate Through Each Customer:

    • Extract arrivalTime and cookingTime for each customer.
    • Update currentTime to the maximum of the current time or the customer's arrival time plus the cooking time.
    • Calculate the waiting time for the current customer and add it to totalWaitingTime.
    for (const customer of customers) {
    let arrivalTime = customer[0];
    let cookingTime = customer[1];
    
    currentTime = Math.max(currentTime, arrivalTime) + cookingTime;
    totalWaitingTime += currentTime - arrivalTime;
}

  3. Calculate and Return Average Waiting Time:

    • Divide totalWaitingTime by the number of customers to get the average waiting time.
    return totalWaitingTime / customers.length;

Complete Code

var averageWaitingTime = function(customers) {
    let totalWaitingTime = 0;
    let currentTime = 0;
    
    for (const customer of customers) {
        let arrivalTime = customer[0];
        let cookingTime = customer[1];
        
        currentTime = Math.max(currentTime, arrivalTime) + cookingTime;
        totalWaitingTime += currentTime - arrivalTime;
    }
    
    return totalWaitingTime / customers.length;
};

Python Solution

Step-by-Step Explanation

  1. Initialize Variables:

    • total_waiting_time to accumulate the total waiting time.
    • current_time to track when the chef is available to start the next order.
    total_waiting_time = 0
current_time = 0

  2. Iterate Through Each Customer:

    • Extract arrival_time and cooking_time for each customer.
    • Update current_time to the maximum of the current time or the customer's arrival time plus the cooking time.
    • Calculate the waiting time for the current customer and add it to total_waiting_time.
    for arrival_time, cooking_time in customers:
    current_time = max(current_time, arrival_time) + cooking_time
    total_waiting_time += current_time - arrival_time

  3. Calculate and Return Average Waiting Time:

    • Divide total_waiting_time by the number of customers to get the average waiting time.
    return total_waiting_time / len(customers)

Complete Code

class Solution:
    def averageWaitingTime(self, customers: List[List[int]]) -> float:
        total_waiting_time = 0
        current_time = 0
        
        for arrival_time, cooking_time in customers:
            current_time = max(current_time, arrival_time) + cooking_time
            total_waiting_time += current_time - arrival_time
        
        return total_waiting_time / len(customers)

Go Solution

Step-by-Step Explanation

  1. Initialize Variables:

    • totalWaitingTime to accumulate the total waiting time.
    • currentTime to track when the chef is available to start the next order.
    totalWaitingTime := 0
currentTime := 0

  2. Iterate Through Each Customer:

    • Extract arrivalTime and cookingTime for each customer.
    • Update currentTime to the maximum of the current time or the customer's arrival time plus the cooking time.
    • Calculate the waiting time for the current customer and add it to totalWaitingTime.
    for _, customer := range customers {
    arrivalTime := customer[0]
    cookingTime := customer[1]
    
    currentTime = max(currentTime, arrivalTime) + cookingTime
    totalWaitingTime += currentTime - arrivalTime
}

  3. Calculate and Return Average Waiting Time:

    • Divide totalWaitingTime by the number of customers to get the average waiting time.
    return float64(totalWaitingTime) / float64(len(customers))

Complete Code

func averageWaitingTime(customers [][]int) float64 {
    totalWaitingTime := 0
    currentTime := 0
    
    for _, customer := range customers {
        arrivalTime := customer[0]
        cookingTime := customer[1]
        
        currentTime = max(currentTime, arrivalTime) + cookingTime
        totalWaitingTime += currentTime - arrivalTime
    }
    
    return float64(totalWaitingTime) / float64(len(customers))
}

func max(a, b int) int {
    if a > b {
        return a
    }
    return b
}

These solutions should help you understand the step-by-step process of solving the LeetCode problem 1701 "Average Waiting Time" in multiple programming languages. Each code snippet is accompanied by a detailed explanation to guide you through the logic and implementation.