第1章 游戏之乐——点游戏

  1 package chapter1youxizhilePointsGame;
  2 
  3 import java.util.Scanner;
  4 
  5 /**
  6  * 点游戏(24点)
  7  * 【解法一】穷举法
  8  * @author DELL
  9  *
 10  */
 11 public class PointsGame1 {
 12     public static final double Precision = 1E-6;  //精度
 13     public static final int CardsNumber = 4;  //牌的数量
 14     public static final int ResultValue = 24; //要求的运算结果值
 15     private double[] number;  //所有可能的四则运算所得到的值，初始为牌的值
 16     private String[] result;  //存放要输出的四则运算结果字符串
 17     //构造函数对数组进行初始化
 18     public PointsGame1(){
 19         number = new double[CardsNumber];
 20         result = new String[CardsNumber];
 21         Scanner input = new Scanner(System.in);
 22         System.out.print("请输入"+CardsNumber+"张牌的值(以空格分隔):");
 23         for(int i=0;i<CardsNumber;i++){
 24             number[i] = input.nextInt();
 25             result[i] = Double.toString(number[i]);
 26         }
 27 
 28     }
 29     /**
 30      * 穷举计算的函数
 31      * @param n 四则运算结果的数量，初始为牌的数量
 32      * @return 是否可以找到对应的运算表达式
 33      */
 34     public boolean pointsGame(int n){
 35         if(n==1){
 36             if(Math.abs(number[0]-ResultValue)<=Precision){
 37                 System.out.println("满足条件的运算表达式为："+result[0]);
 38                 return true;
 39             }else{
 40                 return false;
 41             }
 42         }
 43         for(int i=0;i<n;i++){
 44             for(int j=i+1;j<n;j++){
 45                 double a,b;  //当前取出的两个数
 46                 String expa,expb;  //当前存储的四则运算字符串
 47                 a = number[i];
 48                 b = number[j];
 49                 number[j] = number[n-1];
 50                 
 51                 expa = result[i];
 52                 expb = result[j];
 53                 result[j] = result[n-1];
 54                 //加法运算
 55                 number[i] = a + b;
 56                 result[i] = "("+expa+"+"+expb+")";
 57                 if(pointsGame(n-1))
 58                     return true;
 59                 //减法运算
 60                 number[i] = a - b;
 61                 result[i] = "("+expa+"-"+expb+")";
 62                 if(pointsGame(n-1))
 63                     return true;
 64                 
 65                 number[i] = b - a;
 66                 result[i] = "("+expb+"-"+expa+")";
 67                 if(pointsGame(n-1))
 68                     return true;
 69                 //乘法运算
 70                 number[i] = a * b;
 71                 result[i] = "("+expa+"*"+expb+")";
 72                 if(pointsGame(n-1))
 73                     return true;
 74                 //除法运算
 75                 if(b!=0){
 76                     number[i] = a / b;
 77                     result[i] = "("+expa+"/"+expb+")";
 78                     if(pointsGame(n-1))
 79                         return true;
 80                 }
 81                 
 82                 if(a!=0){
 83                     number[i] = b / a;
 84                     result[i] = "("+expb+"/"+expa+")";
 85                     if(pointsGame(n-1))
 86                         return true;
 87                 }
 88                 //如果还没找到，就恢复原来的状态继续下一轮搜索
 89                 number[i] = a;
 90                 number[j] = b;
 91                 result[i] = expa;
 92                 result[j] = expb;
 93             }
 94         }
 95         return false;
 96     }
 97     
 98     public static void main(String[] args) {
 99         PointsGame1 pg = new PointsGame1();
100         if(pg.pointsGame(CardsNumber)){
101             System.out.println("构造成功！");
102         }else
103             System.out.println("构造失败！");
104     }
105 
106 }

请输入4张牌的值(以空格分隔):11 8 3 5
满足条件的运算表达式为：(((11.0-8.0)+5.0)*3.0)
构造成功！