Introduction

In this blog post, we will explore how to solve the LeetCode problem "2391" using AI. LeetCode is a popular platform for preparing for coding interviews, and with the help of AI tools like Chatmagic, we can generate solutions quickly and efficiently - helping you pass the interviews and get the job offer without having to study for months.

Problem Statement

You are given a 0-indexed array of strings garbage where garbage[i] represents the assortment of garbage at the ith house. garbage[i] consists only of the characters 'M', 'P' and 'G' representing one unit of metal, paper and glass garbage respectively. Picking up one unit of any type of garbage takes 1 minute. You are also given a 0-indexed integer array travel where travel[i] is the number of minutes needed to go from house i to house i + 1. There are three garbage trucks in the city, each responsible for picking up one type of garbage. Each garbage truck starts at house 0 and must visit each house in order; however, they do not need to visit every house. Only one garbage truck may be used at any given moment. While one truck is driving or picking up garbage, the other two trucks cannot do anything. Return the minimum number of minutes needed to pick up all the garbage. Example 1: Input: garbage = ["G","P","GP","GG"], travel = [2,4,3] Output: 21 Explanation: The paper garbage truck: 1. Travels from house 0 to house 1 2. Collects the paper garbage at house 1 3. Travels from house 1 to house 2 4. Collects the paper garbage at house 2 Altogether, it takes 8 minutes to pick up all the paper garbage. The glass garbage truck: 1. Collects the glass garbage at house 0 2. Travels from house 0 to house 1 3. Travels from house 1 to house 2 4. Collects the glass garbage at house 2 5. Travels from house 2 to house 3 6. Collects the glass garbage at house 3 Altogether, it takes 13 minutes to pick up all the glass garbage. Since there is no metal garbage, we do not need to consider the metal garbage truck. Therefore, it takes a total of 8 + 13 = 21 minutes to collect all the garbage. Example 2: Input: garbage = ["MMM","PGM","GP"], travel = [3,10] Output: 37 Explanation: The metal garbage truck takes 7 minutes to pick up all the metal garbage. The paper garbage truck takes 15 minutes to pick up all the paper garbage. The glass garbage truck takes 15 minutes to pick up all the glass garbage. It takes a total of 7 + 15 + 15 = 37 minutes to collect all the garbage. Constraints: 2 <= garbage.length <= 105 garbage[i] consists of only the letters 'M', 'P', and 'G'. 1 <= garbage[i].length <= 10 travel.length == garbage.length - 1 1 <= travel[i] <= 100

Explanation

Here's the solution:

• Calculate Garbage Collection Time: Iterate through each garbage type ('M', 'P', 'G') and compute the total time spent picking up that type of garbage across all houses.
• Calculate Travel Time: For each garbage type, find the last house it visits. Calculate the travel time up to that house only, as there's no need to travel further if a type of garbage is not present.

• Sum the Times: Add the total collection times and the relevant travel times for each of the three garbage types to get the final result.

• Runtime Complexity: O(N*M), where N is the number of houses and M is the maximum length of the garbage string at a given house.

• Storage Complexity: O(1)

Code

    def garbageCollection(garbage, travel):
    """
    Calculates the minimum time to collect all garbage.

    Args:
        garbage: A list of strings representing the garbage at each house.
        travel: A list of integers representing the travel time between houses.

    Returns:
        The minimum time needed to collect all the garbage.
    """

    garbage_types = ['M', 'P', 'G']
    total_time = 0
    last_house = {}

    for g_type in garbage_types:
        last_house[g_type] = -1

    for i in range(len(garbage)):
        for g_type in garbage_types:
            if g_type in garbage[i]:
                last_house[g_type] = i
        total_time += len(garbage[i])  # Add collection time

    travel_time = 0
    for g_type in garbage_types:
        last = last_house[g_type]
        if last > 0:
            travel_time += sum(travel[:last])

    return total_time + travel_time