Building Leaderboards with C# Collections

using System;
using System.Collections.Generic;
using System.Linq;

class Leaderboard
{
    private SortedDictionary<int, List<string>> scores = new SortedDictionary<int, List<string>>(Comparer<int>.Create((x, y) => y.CompareTo(x)));

    public void AddScore(string user, int score)
    {
        if (!scores.ContainsKey(score))
        {
            scores[score] = new List<string>();
        }
        scores[score].Add(user);
    }
    
    public List<(string, int)> GetLeaderboard(int topN)
    {
        var leaderboard = new List<(string, int)>();
        foreach (var score in scores)
        {
            foreach (var user in score.Value)
            {
                if (leaderboard.Count < topN)
                {
                    leaderboard.Add((user, score.Key));
                }
                else
                {
                    return leaderboard;
                }
            }
        }
        return leaderboard;
    }

    public (int rank, int score) GetUserRankAndScore(string user)
    {
        int rank = 0;
        foreach (var entry in scores)
        {
            rank += entry.Value.Count;
            if (entry.Value.Contains(user))
            {
                return (rank - entry.Value.Count + entry.Value.IndexOf(user) + 1, entry.Key);
            }
        }
        return (-1, -1); // User not found
    }
}

class Program
{
    static void Main()
    {
        var leaderboard = new Leaderboard();
        leaderboard.AddScore("user1", 100);
        leaderboard.AddScore("user2", 200);
        leaderboard.AddScore("user3", 150);

        var topUsers = leaderboard.GetLeaderboard(3);
        Console.WriteLine("Top Users:");
        foreach (var user in topUsers)
        {
            Console.WriteLine($"User: {user.Item1}, Score: {user.Item2}");
        }

        var userRankScore = leaderboard.GetUserRankAndScore("user3");
        Console.WriteLine($"User3's Rank: {userRankScore.rank}, Score: {userRankScore.score}");
    }
}