Introduction

In this blog post, we will explore how to solve the LeetCode problem "2491" 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 positive integer array skill of even length n where skill[i] denotes the skill of the ith player. Divide the players into n / 2 teams of size 2 such that the total skill of each team is equal. The chemistry of a team is equal to the product of the skills of the players on that team. Return the sum of the chemistry of all the teams, or return -1 if there is no way to divide the players into teams such that the total skill of each team is equal. Example 1: Input: skill = [3,2,5,1,3,4] Output: 22 Explanation: Divide the players into the following teams: (1, 5), (2, 4), (3, 3), where each team has a total skill of 6. The sum of the chemistry of all the teams is: 1 5 + 2 4 + 3 3 = 5 + 8 + 9 = 22. Example 2: Input: skill = [3,4] Output: 12 Explanation: The two players form a team with a total skill of 7. The chemistry of the team is 3 4 = 12. Example 3: Input: skill = [1,1,2,3] Output: -1 Explanation: There is no way to divide the players into teams such that the total skill of each team is equal. Constraints: 2 <= skill.length <= 105 skill.length is even. 1 <= skill[i] <= 1000

Explanation

Here's the breakdown of the solution:

• Find the Target Sum: Calculate the desired skill sum for each team by summing all skills and dividing by the number of teams (n / 2). If the total skill isn't evenly divisible by the number of teams, it's impossible to form valid teams.
• Use a Hash Map (Counter): Use a hash map (Counter in Python) to store the frequency of each skill level. Iterate through the skills. For each skill, check if its complement (target sum - skill) exists in the hash map. If it does, decrement the counts of both skills, calculate the chemistry, and add it to the total.

• Check for Validity: If at any point, a skill's complement isn't found or its count becomes negative, it's impossible to form valid teams.

• Runtime Complexity: O(n), where n is the length of the skill array.

• Storage Complexity: O(k), where k is the number of unique skill values. In the worst case, where all skills are unique, k could be close to n.

Code

    from collections import Counter

def dividePlayers(skill):
    n = len(skill)
    total_skill = sum(skill)
    num_teams = n // 2

    if total_skill % num_teams != 0:
        return -1

    target_sum = total_skill // num_teams
    chemistry_sum = 0
    skill_counts = Counter(skill)

    for s in skill:
        if skill_counts[s] > 0:
            complement = target_sum - s
            if skill_counts[complement] > 0:
                chemistry_sum += s * complement
                skill_counts[s] -= 1
                skill_counts[complement] -= 1
            else:
                return -1

    return chemistry_sum // 2