一，游戏介绍

1.1 游戏规则

21点又名黑杰克，该游戏由2到6个人玩，使用除大小王之外的52张牌，游戏者的目标是使手中的牌的点数之和不超过21点且尽量大。

1.2 牌点计算

A至10牌，按其原点数计算；J、Q、K都算作10点。

1.3 判断胜负

二十一点玩法规则和概率在二十一点游戏中，拥有最高点数的玩家获胜，其点数必须等于或低于21点；超过21点的玩家称为爆牌。拥有最高点数的玩家获胜，其点数必须等于或低于21点；超过21点之间判负。

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二，游戏设计

2.1 游戏流程

1. 发牌：
   玩家和AI每人发两张牌，由手牌点数和大的玩家优先选择是否在牌堆中取牌

2. 取牌：
   手牌点数和小于21，等待1中优先选择后再顺时针轮到其他玩家选择是否取牌

3. 取牌后：
   若牌点大于21则直接判负出局，场上只剩1人，直接游戏结束；否则重复2-3
   若牌点小于等于21则轮到下家取牌，重复2-3

4. 游戏结束
   其他玩家取牌后都超过21点，只剩1人，直接获胜
   所有玩家都选择不取牌后，按规则比较所有玩家手牌点数和，牌点大的获胜。

2.2 玩家类

由玩家自己选择是否继续拿牌。（输入Y继续拿牌，N为不拿牌）

2.3 AI类

简化AI逻辑，发牌后AI手牌和为4-8时继续拿牌，一直到17点或17点以上不再拿牌；因为此时再拿牌就有一半以上的概率超过21点。

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三，参考代码

using System;

namespace _21dian
{
    using System;
    using System.Collections.Generic;

    namespace Game21Points
    {
        class Project
        {
            static void Main(string[] args)
            {
                Console.WriteLine("----- 游戏开始 -----");

                // 扑克牌
                List<int> cards = new List<int>()
                {
                    1,  2,  3,  4,  5,  6,  7,  8,  9,  10, 11, 12, 13,
                    14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26,
                    27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39,
                    40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52
                };

                // 创建对象
                Poker poker = new Poker(cards);
                Player player = new Player();
                AIPlayer ai = new AIPlayer();

                // --> 玩家入场
                player.playerName = "Czhenya";
                ai.playerName = "AI";

                poker.AddPlayer(player);
                poker.AddPlayer(ai);

                // 事件关系绑定
                poker.GameSratrHandler += player.GameStart;
                poker.GameSratrHandler += ai.GameStart;

                // 游戏开始 
                poker.GameStart();

                // 每人发两张牌
                poker.SendCard();
                poker.SendCard();

                // 询问取牌
                poker.TaskCard();

                Console.ReadKey();
            }
        }

        abstract class AbsPlayer
        {
            public string playerName;
            public bool IsContinueTakeCard = true;
            public List<int> handCards = new List<int>();

            public abstract void GameStart();

            public virtual void SendCard(int card)
            {
                handCards.Add(card);
            }

            public abstract bool TakeCard();

            public bool GameOver()
            {
                bool isGameOver;
                if (HandCardsPoint > 21)
                {
                    isGameOver = true;
                }
                else
                {
                    isGameOver = !IsContinueTakeCard;
                }
                return isGameOver;
            }

            public int HandCardsPoint { get { return PokeTools.HandCardsSum(handCards); } }
        }

        class Player : AbsPlayer
        {
            public override void GameStart()
            {
                handCards.Clear();
                Console.WriteLine("玩家整理了一下衣服，准备开局；");
            }

            public override void SendCard(int card)
            {
                handCards.Add(card);
                Console.WriteLine("玩家发牌：" + PokeTools.PokerBrandByPoint(card));
            }

            public override bool TakeCard()
            {
                Console.WriteLine("当前您的手牌点数和为：" + HandCardsPoint);
                Console.WriteLine("是否继续取牌(Y/N)？");
                string readStr = Console.ReadLine();
                // 输入Y取牌，其他为不取牌
                IsContinueTakeCard = readStr.Equals("Y");
                return IsContinueTakeCard;
            }
        }

        class AIPlayer : AbsPlayer
        {
            public override void GameStart()
            {
                handCards.Clear();
                Console.WriteLine("AI：清理一下内存，与之一战；");
            }

            public override void SendCard(int card)
            {
                base.SendCard(card);
                Console.WriteLine("AI发牌：" + PokeTools.PokerBrandByPoint(card));
            }

            public override bool TakeCard()
            {
                // 手牌数点数小于17，就继续取牌
                return HandCardsPoint < 17;
            }
        }

        class Poker
        {
            List<AbsPlayer> players = new List<AbsPlayer>();
            public Action GameSratrHandler;
            public Action<int> SendCardHandler;
            public Func<int, bool> TaskCardHandler;
            // 发牌用
            List<int> sendCards;

            public Poker(List<int> cards)
            {
                // 复制一份发牌用
                sendCards = new List<int>(cards);
            }

            public void AddPlayer(AbsPlayer player)
            {
                players.Add(player);
            }

            public void GameStart()
            {
                for (int i = 0; i < players.Count; i++)
                {
                    if (!players[i].GameOver())
                    {
                        players[i].GameStart();
                    }
                }
            }

            /// 

            /// 发牌 -- 会剔除已经发过的牌
            /// 
            public void SendCard()
            {
                for (int i = 0; i < players.Count; i++)
                {
                    players[i].SendCard(SendOneCard());
                }
            }

            int SendOneCard()
            {
                // 随机发一张牌
                Random random = new Random();
                int index = random.Next(0, sendCards.Count);
                // 取到牌值
                int cardPoint = sendCards[index];
                // 从手牌中移除 --> 为避免发到相同的牌
                sendCards.RemoveAt(index);

                return cardPoint;
            }

            public void TaskCard()
            {
                for (int i = 0; i < players.Count; i++)
                {
                    // 选择取牌后再发一张牌
                    if (players[i].TakeCard())
                    {
                        players[i].SendCard(SendOneCard());
                    }
                    Console.WriteLine($"玩家：{players[i].playerName} 手牌：{PokeTools.ShowHandCard(players[i].handCards)}");
                }

                if (!GameOver())
                {
                    TaskCard();
                }
            }

            public bool GameOver()
            {
                int playerCount = 0;
                for (int i = 0; i < players.Count; i++)
                {
                    if (!players[i].GameOver())
                    {
                        playerCount++;
                    }
                }

                bool isGameOver = playerCount <= 1;

                if (isGameOver)
                {
                    Console.WriteLine("游戏结束：");

                    List<AbsPlayer> playerList = new List<AbsPlayer>();
                    int maxPoint = 0;
                    for (int i = 0; i < players.Count; i++)
                    {
                        if (players[i].HandCardsPoint > 21)
                        {
                            Console.WriteLine($"玩家：{players[i].playerName} 爆牌了"  );
                        }
                        else
                        {
                            playerList.Add(players[i]);
                            if (maxPoint < players[i].HandCardsPoint)
                            {
                                maxPoint = players[i].HandCardsPoint;
                            }
                        }
                    }

                    if (playerList.Count == 0)
                    {
                        Console.WriteLine("平局");
                    } 
                    else if (playerList.Count == 1)
                    {

                        Console.WriteLine($"玩家：{playerList[0].playerName} 赢了");
                    }
                    else
                    {
                        for (int i = 0; i < playerList.Count; i++)
                        {
                            if (maxPoint == playerList[i].HandCardsPoint)
                            {
                                Console.WriteLine($"玩家：{playerList[i].playerName} 赢了");
                            }
                        }
                    }
                }
                return isGameOver;
            }
        }
    }

    class PokeTools
    {
        /// 

        /// 根据牌点返回牌名 如：14 ->红桃3
        /// 
        /// 
        /// 
        public static string PokerBrandByPoint(int card)
        {
            if (card > 52 || card <= 0)
            {
                Console.WriteLine("不是扑克牌点");
                return "不是扑克牌点";
            }

            string[] flowerColor = new string[4] { "黑桃", "红桃", "梅花", "方片" };
            string[] points = new string[13] { "K", "A", "2", "3", "4", "5", "6", "7", "8", "9", "10", "J", "Q" };
            int huaSe = (card - 1) / 13;
            int point = card % 13;

            // 返回花色 + 牌点 如：红桃3
            return flowerColor[huaSe] + points[point];
        }

        /// 

        /// 手牌求和
        /// 
        /// 
        /// 
        public static int HandCardsSum(List<int> handCards)
        {
            // "K", "2", "3", "4", "5", "6", "7", "8", "9", "10", "J", "Q"
            int[] points = new int[13] { 10, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 10, 10 };
            int sumRes = 0;

            for (int i = 0; i < handCards.Count; i++)
            {
                sumRes += points[handCards[i] % 13];
            }

            return sumRes;
        }

        // 显示手牌
        public static (string, string) ShowHandCard(List<int> handCards)
        {
            string resStr = "";
            for (int i = 0; i < handCards.Count; i++)
            {
                resStr += PokeTools.PokerBrandByPoint(handCards[i]);
                if (handCards.Count - 1 != i)
                {
                    resStr += ",";
                }
            }

            return (resStr, "牌点和:" + PokeTools.HandCardsSum(handCards));
        }
    }
}
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测试结果：

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