Lobby and matchmaking basics in Unity - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this lobby player count code?

Consider this Unity C# code snippet that manages a lobby's player count. What will be printed to the console?

Unity

using UnityEngine;
using System.Collections.Generic;

public class LobbyManager : MonoBehaviour {
    private List<string> players = new List<string>();

    void Start() {
        players.Add("Alice");
        players.Add("Bob");
        players.Remove("Alice");
        Debug.Log($"Players in lobby: {players.Count}");
    }
}

A Players in lobby: 1

B Players in lobby: 2

C Players in lobby: 0

D Players in lobby: 3

💡 Hint

Think about how many players are added and removed before the count is printed.

Two players are added: Alice and Bob. Then Alice is removed. So only Bob remains, making the count 1.

🧠 Conceptual

intermediate

Which statement best describes matchmaking in Unity?

Matchmaking helps players find games to join. Which option correctly describes its main purpose?

A It matches players based on criteria like skill or region to create balanced games.

B It connects players to random game servers without any filtering.

C It only allows players to join games created by their friends.

D It automatically creates new game servers for every player joining.

💡 Hint

Think about why matchmaking is important for player experience.

Matchmaking aims to create fair and enjoyable games by grouping players with similar skill or location.

🔧 Debug

advanced

Why does this lobby join code cause a runtime error?

Look at this code snippet that tries to join a lobby. What causes the runtime error?

Unity

using UnityEngine;

public class LobbyJoiner : MonoBehaviour {
    string lobbyId = null;

    void JoinLobby() {
        Debug.Log($"Joining lobby {lobbyId.ToUpper()}");
    }

    void Start() {
        JoinLobby();
    }
}

A The lobbyId variable is not initialized with a valid lobby name.

B The method JoinLobby is private and cannot be called from Start.

C Debug.Log cannot use string interpolation in Unity.

D lobbyId is null, so calling ToUpper() causes a NullReferenceException.

💡 Hint

Check what happens when you call a method on a null string.

Since lobbyId is null, calling ToUpper() on it causes a NullReferenceException at runtime.

📝 Syntax

advanced

Which option correctly declares a lobby dictionary with player counts?

You want to create a dictionary in C# that maps lobby names (strings) to player counts (integers). Which declaration is correct?

A Dictionary lobbies = new Dictionary<string, int>();

B Dictionary<string, int> lobbies = new Dictionary<string, int>();

C Dictionary<string> lobbies = new Dictionary<string>();

D Dictionary<int, string> lobbies = new Dictionary<int, string>();

💡 Hint

Remember the syntax for generic dictionaries in C#.

Option B correctly declares a dictionary with string keys and int values.

🚀 Application

expert

What is the final player count after this matchmaking simulation?

Given this code simulating players joining and leaving a lobby, what is the final count printed?

Unity

using System.Collections.Generic;
using UnityEngine;

public class MatchmakingSim : MonoBehaviour {
    List<string> players = new List<string>();

    void Simulate() {
        players.Add("Anna");
        players.Add("Ben");
        players.Add("Cara");
        players.RemoveAt(1);
        players.Add("Dan");
        players.Remove("Anna");
        Debug.Log($"Final players: {players.Count}");
    }

    void Start() {
        Simulate();
    }
}

A Final players: 4

B Final players: 1

C Final players: 2

D Final players: 3

💡 Hint

Track each add and remove step carefully.

Players added: Anna, Ben, Cara (3). RemoveAt(1) removes Ben (2 left). Add Dan (3). Remove Anna (2 left). Final count is 2.