Introduction

In this blog post, we will explore how to solve the LeetCode problem "3207" 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 an integer array enemyEnergies denoting the energy values of various enemies. You are also given an integer currentEnergy denoting the amount of energy you have initially. You start with 0 points, and all the enemies are unmarked initially. You can perform either of the following operations zero or multiple times to gain points: Choose an unmarked enemy, i, such that currentEnergy >= enemyEnergies[i]. By choosing this option: You gain 1 point. Your energy is reduced by the enemy's energy, i.e. currentEnergy = currentEnergy - enemyEnergies[i]. If you have at least 1 point, you can choose an unmarked enemy, i. By choosing this option: Your energy increases by the enemy's energy, i.e. currentEnergy = currentEnergy + enemyEnergies[i]. The enemy i is marked. Return an integer denoting the maximum points you can get in the end by optimally performing operations. Example 1: Input: enemyEnergies = [3,2,2], currentEnergy = 2 Output: 3 Explanation: The following operations can be performed to get 3 points, which is the maximum: First operation on enemy 1: points increases by 1, and currentEnergy decreases by 2. So, points = 1, and currentEnergy = 0. Second operation on enemy 0: currentEnergy increases by 3, and enemy 0 is marked. So, points = 1, currentEnergy = 3, and marked enemies = [0]. First operation on enemy 2: points increases by 1, and currentEnergy decreases by 2. So, points = 2, currentEnergy = 1, and marked enemies = [0]. Second operation on enemy 2: currentEnergy increases by 2, and enemy 2 is marked. So, points = 2, currentEnergy = 3, and marked enemies = [0, 2]. First operation on enemy 1: points increases by 1, and currentEnergy decreases by 2. So, points = 3, currentEnergy = 1, and marked enemies = [0, 2]. Example 2: Input: enemyEnergies = [2], currentEnergy = 10 Output: 5 Explanation: Performing the first operation 5 times on enemy 0 results in the maximum number of points. Constraints: 1 <= enemyEnergies.length <= 105 1 <= enemyEnergies[i] <= 109 0 <= currentEnergy <= 109

Explanation

Here's the breakdown of the approach, complexity, and the Python code:

• High-Level Approach:

  • Prioritize defeating enemies with lower energies first to maximize the number of enemies defeated initially, thereby getting more points. Sort the enemy energies in ascending order.
  • After getting at least one point, strategically mark enemies to increase energy and defeat more enemies later. Consider the trade-offs between marking enemies and directly defeating them based on current energy levels.
  • In case all initial enemies can be defeated directly, we can infinitely defeat the enemy with the lowest energy.

• Complexity:

  • Runtime Complexity: O(N log N) due to sorting, where N is the number of enemies.
  • Storage Complexity: O(1) (excluding the input array), as we are using a constant amount of extra space.

Code

    def max_points(enemyEnergies, currentEnergy):
    """
    Calculates the maximum points achievable by defeating enemies.

    Args:
        enemyEnergies: A list of integers representing enemy energies.
        currentEnergy: An integer representing the initial energy.

    Returns:
        An integer representing the maximum achievable points.
    """

    enemyEnergies.sort()
    points = 0
    marked = set()
    n = len(enemyEnergies)

    i = 0
    while i < n:
        if currentEnergy >= enemyEnergies[i]:
            currentEnergy -= enemyEnergies[i]
            points += 1
            i += 1
        else:
            if points > 0:
                # Try to find the smallest marked enemy to unmark
                if marked:
                    min_marked_energy = float('inf')
                    min_marked_index = -1
                    for index in marked:
                        if enemyEnergies[index] < min_marked_energy:
                            min_marked_energy = enemyEnergies[index]
                            min_marked_index = index

                    if min_marked_index != -1:
                        currentEnergy += enemyEnergies[min_marked_index]
                        marked.remove(min_marked_index)
                else:
                    return points  # Not possible to gain energy, and we're stuck

                # Check if we can defeat current enemy
                if currentEnergy >= enemyEnergies[i]:
                    continue
                else:
                    return points # No way to defeat more enemies

            else:
                #Not possible to defeat initial enemies
                return 0

    #If all initial enemies can be defeated.
    if n>0:
        points += currentEnergy // enemyEnergies[0]

    return points