C#实现的24点游戏实例详解

本文实例分析了C#实现的24点游戏。分享给大家供大家参考。具体如下：

1. 24点游戏规则及算法

规则：给出4个自然数，找出能够求出24的四则运算式，要求数字不能重复使用
分析：

本算法是一种暴力求解法：

给出任意两个数字，可以进行6种四则运算，求出最多6个值。以数字a和b为例，有：

加（a+b）、减（a-b）、被减（b-a）、乘以（a*b）、除以(a/b)和除(b/a)
abcd共计四个数，如果顺序固定，则有5种计算顺序（★代表上面6种四则运算中的一种）：

((a★b)★c)★d、(a★b)★(c★d)、(a★(b★c))★d、a★((b★c)★d)、a★(b★(c★d))

给出的四个数字，n1n2n3n4，有4*3*2=24种全排列的方法

2. 相关函数

/// <summary>
/// 判断abcd四个数进行任意四则运算后能不能得出24，每个数字只能用一次
/// </summary>
/// <param name="a">数字a</param>
/// <param name="b">数字b</param>
/// <param name="c">数字c</param>
/// <param name="d">数字d</param>
/// <param name="expression"></param>
/// <returns></returns>
private static bool Try24(int a, int b, int c, int d, ref string expression)
{
 //a字头
 if (TryEach(a, b, c, d, ref expression)) return true;
 if (TryEach(a, b, d, c, ref expression)) return true;
 if (TryEach(a, c, b, d, ref expression)) return true;
 if (TryEach(a, c, d, b, ref expression)) return true;
 if (TryEach(a, d, b, c, ref expression)) return true;
 if (TryEach(a, d, c, b, ref expression)) return true;
 //b字头
 if (TryEach(b, a, c, d, ref expression)) return true;
 if (TryEach(b, a, d, c, ref expression)) return true;
 if (TryEach(b, c, a, d, ref expression)) return true;
 if (TryEach(b, c, d, a, ref expression)) return true;
 if (TryEach(b, d, a, c, ref expression)) return true;
 if (TryEach(b, d, c, a, ref expression)) return true;
 //c字头
 if (TryEach(c, a, b, d, ref expression)) return true;
 if (TryEach(c, a, d, b, ref expression)) return true;
 if (TryEach(c, b, a, c, ref expression)) return true;
 if (TryEach(c, b, c, a, ref expression)) return true;
 if (TryEach(c, d, a, b, ref expression)) return true;
 if (TryEach(c, d, b, a, ref expression)) return true;
 //d字头
 if (TryEach(d, a, b, c, ref expression)) return true;
 if (TryEach(d, a, c, b, ref expression)) return true;
 if (TryEach(d, b, a, c, ref expression)) return true;
 if (TryEach(d, b, c, a, ref expression)) return true;
 if (TryEach(d, c, a, b, ref expression)) return true;
 if (TryEach(d, c, b, a, ref expression)) return true;
 return false;
}
/// <summary>
/// 判断指定顺序的四个数abcd进行任意四则运算后能不能得出24，每个数字只能用一次
/// </summary>
/// <param name="a">数字1</param>
/// <param name="b">数字2</param>
/// <param name="c">数字3</param>
/// <param name="d">数字4</param>
/// <param name="expression"></param>
/// <returns></returns>
private static bool TryEach(int a, int b, int c, int d, ref string expression)
{
 expression = "";
 //两个数可以做6种运算：加、减、被减、乘以、除以、除
 //四个数共可以进行6*6*6=216种不同次序的四则运算
 //初始化数组
 for (int i = 0; i < 6 * 6 * 6; i++)
 {
  //a与b间的运算符：i / 36
  //b与c间的运算符：i % 36 / 6
  //c与d间的运算符：i % 6
  //1.运算顺序：a和b，再和c，再和d
  {
   string expression1 = "", expression2 = "";
   int temp1 = ResultOf(a, b, i / 36, ref expression1);
   int temp2 = ResultOf(temp1, c, i % 36 / 6, ref expression2, expression1);
   int result = ResultOf(temp2, d, i % 6, ref expression, expression2);
   if (result == 24) return true;
  }
  //2.运算顺序：a和b，c和d，前面部分和后面部分
  {
   string expression1 = "", expression2 = "";
   int temp1 = ResultOf(a, b, i / 36, ref expression1);
   int temp2 = ResultOf(c, d, i % 6, ref expression2);
   int result = ResultOf(temp1, temp2, i % 36 / 6,
    ref expression, expression1, expression2);
   if (result == 24) return true;
  }
  //3.运算顺序：b和c运算，再与a运算，再与d运算
  {
   string expression1 = "", expression2 = "";
   int temp1 = ResultOf(b, c, i % 36 / 6, ref expression1);
   int temp2 = ResultOf(a, temp1, i / 36, ref expression2, "", expression1);
   int result = ResultOf(temp2, d, i % 6, ref expression, expression2);
   if (result == 24) return true;
  }
  //4.运算顺序：b和c运算，再与d运算，再与a运算
  {
   string expression1 = "", expression2 = "";
   int temp1 = ResultOf(b, c, i % 36 / 6, ref expression1);
   int temp2 = ResultOf(temp1, d, i % 6, ref expression2, expression1);
   int result = ResultOf(a, temp2, i / 36, ref expression, "", expression2);
   if (result == 24) return true;
  }
  //5.运算顺序：c和d运算，再和b运算，再和a运算
  {
   string expression1 = "", expression2 = "";
   int temp1 = ResultOf(c, d, i % 6, ref expression1);
   int temp2 = ResultOf(b, temp1, i % 36 / 6, ref expression2, "", expression1);
   int result = ResultOf(a, temp2, i / 36, ref expression, "", expression2);
   if (result == 24) return true;
  }
 }
 expression = "Abandoned";
 return false;
}
/// <summary>
/// 求两数进行某一四则运算后的结果
/// </summary>
/// <param name="x">数字1</param>
/// <param name="y">数字2</param>
/// <param name="method">（0-5分别代表：加、减、被减、乘以、除以、除）</param>
/// <param name="expression">返回的表达式</param>
/// <param name="expressionLeft">数字1表达式</param>
/// <param name="expressionRight">数字2表达式</param>
/// <returns></returns>
private static int ResultOf(int x, int y, int method,
 ref string expression, string expressionLeft = "", string expressionRight = "")
{
 //左右表达式之前被判定为无效则不计算，除数为0时不计算
 if (expressionLeft == "Abandoned" || expressionRight == "Abandoned" ||
  (x == 0 && method == 5) || (y == 0 && method == 4))
 {
  expression = "Abandoned";
  return -1;
 }
 int result = 0;
 switch (method)
 {
  case 0:
   {
    //加
    result = x + y;
    expression = string.Format("{0}+{1}",
     expressionLeft == "" ? x.ToString() : expressionLeft,
     expressionRight == "" ? y.ToString() : expressionRight);
   }
   break;
  case 1:
   {
    //减
    result = x - y;
    expression = string.Format("{0}-{1}",
     expressionLeft == "" ? x.ToString() : expressionLeft,
     expressionRight == "" ? y.ToString() : expressionRight);
   }
   break;
  case 2:
   {
    //被减
    result = y - x;
    expression = string.Format("{1}-{0}",
     expressionLeft == "" ? x.ToString() : expressionLeft,
     expressionRight == "" ? y.ToString() : expressionRight);
   }
   break;
  case 3:
   {
    //乘以
    result = x * y;
    expression = string.Format("({0})*({1})",
     expressionLeft == "" ? x.ToString() : expressionLeft,
     expressionRight == "" ? y.ToString() : expressionRight);
   }
   break;
  case 4:
   {
    //除以
    if (x % y == 0)
    {
     result = x / y;
     expression = string.Format("({0})/({1})",
      expressionLeft == "" ? x.ToString() : expressionLeft,
      expressionRight == "" ? y.ToString() : expressionRight);
    }
    else
    {
     expression = "Abandoned";
    }
   }
   break;
  case 5:
   {
    //除
    if (y % x == 0)
    {
     result = y / x;
     expression = string.Format("({1})/({0})",
      expressionLeft == "" ? x.ToString() : expressionLeft,
      expressionRight == "" ? y.ToString() : expressionRight);
    }
    else
    {
     expression = "Abandoned";
    }
   }
   break;
 }
 //运算不合法，则返回-1，表达式为Abandoned，
 if (expression == "Abandoned")
 {
  return -1;
 }
 return result;
}

3. Main函数调用

static void Main(string[] args)