Introduction

In this blog post, we will explore how to solve the LeetCode problem "1921" 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 playing a video game where you are defending your city from a group of n monsters. You are given a 0-indexed integer array dist of size n, where dist[i] is the initial distance in kilometers of the ith monster from the city. The monsters walk toward the city at a constant speed. The speed of each monster is given to you in an integer array speed of size n, where speed[i] is the speed of the ith monster in kilometers per minute. You have a weapon that, once fully charged, can eliminate a single monster. However, the weapon takes one minute to charge. The weapon is fully charged at the very start. You lose when any monster reaches your city. If a monster reaches the city at the exact moment the weapon is fully charged, it counts as a loss, and the game ends before you can use your weapon. Return the maximum number of monsters that you can eliminate before you lose, or n if you can eliminate all the monsters before they reach the city. Example 1: Input: dist = [1,3,4], speed = [1,1,1] Output: 3 Explanation: In the beginning, the distances of the monsters are [1,3,4]. You eliminate the first monster. After a minute, the distances of the monsters are [X,2,3]. You eliminate the second monster. After a minute, the distances of the monsters are [X,X,2]. You eliminate the third monster. All 3 monsters can be eliminated. Example 2: Input: dist = [1,1,2,3], speed = [1,1,1,1] Output: 1 Explanation: In the beginning, the distances of the monsters are [1,1,2,3]. You eliminate the first monster. After a minute, the distances of the monsters are [X,0,1,2], so you lose. You can only eliminate 1 monster. Example 3: Input: dist = [3,2,4], speed = [5,3,2] Output: 1 Explanation: In the beginning, the distances of the monsters are [3,2,4]. You eliminate the first monster. After a minute, the distances of the monsters are [X,0,2], so you lose. You can only eliminate 1 monster. Constraints: n == dist.length == speed.length 1 <= n <= 105 1 <= dist[i], speed[i] <= 105

Explanation

Here's the solution to the monster elimination problem:

• Calculate arrival times: Compute the time each monster takes to reach the city (dist[i] / speed[i]).
• Sort arrival times: Sort the arrival times in ascending order. This allows us to prioritize eliminating monsters that arrive sooner.

• Simulate elimination: Iterate through the sorted arrival times. If a monster arrives before the current time (number of eliminated monsters), we lose. Otherwise, we eliminate the monster and increment the time.

• Runtime Complexity: O(n log n) due to sorting. Storage Complexity: O(n) to store the arrival times.

Code

    def eliminateMaximum(dist, speed):
    n = len(dist)
    arrival_times = []
    for i in range(n):
        arrival_times.append((dist[i] + speed[i] - 1) // speed[i])  # Use ceiling division to round up

    arrival_times.sort()

    eliminated = 0
    time = 0

    for arrival_time in arrival_times:
        if arrival_time <= time:
            return eliminated
        else:
            eliminated += 1
            time += 1

    return eliminated