using System;

using System.Collections.Generic;

public class Program

{

    public static void Main()

    {

        PlayerState p = new PlayerState("idle");

        UI ui1 = new UI(p, "UI1");

        UI ui2 = new UI(p, "UI2");

​

        p.SetPlayerState("Attacking");

        p.SetPlayerState("Defending");

        p.RemoveObserver(ui1);

        p.SetPlayerState("None");

​

​

    }

}

​

public interface Subject

{

    void AddObserver(Observer o);

    void RemoveObserver(Observer o);

    void NotifyObservers();

}

​

public interface Observer

{

    void Update();

}

​

public class PlayerState : Subject

{

    List<Observer> observers;

    string state;

    public PlayerState(string state)

    {

        this.state = state;

        observers = new List<Observer>();

    }

​

    public void AddObserver(Observer o)

    {

        observers.Add(o);

    }

    public void RemoveObserver(Observer o)

    {

        observers.Remove(o);

    }

    public void NotifyObservers()

    {

        foreach(Observer o in observers)

        {

            o.Update();

        }

    }

    public void SetPlayerState(string newState)

    {

        state = newState;

        NotifyObservers();

    }

    public string GetPlayerState()

    {

        return state;

    }

}

​

public class UI : Observer

{

    PlayerState playerStateObj;

    string playerState;

    string name;

    public UI(PlayerState s, string name)

    {

        playerStateObj = s;

        this.name = name;

        playerStateObj.AddObserver(this);

    }

    public void Update()

    {

        playerState = playerStateObj.GetPlayerState();

        Display();

    }

    public void Display()

    {

        if(playerState == "Attacking")

        {

            Console.WriteLine(name + " shows attack menu");

        }

        else if(playerState == "Defending")

        {

            Console.WriteLine(name + " shows defend menu");

        }

        else

        {

            Console.WriteLine(name + " shows idle menu");

        }

    }

}