一个求24点的算法

一个求24点的算法

 

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace _24Point
{
    class Program
    {
        /**//*
         * a b c d (1 - 10)
         * x y z (+ - * /)
         * axbyczd有无种情况，逆波兰表达式
         * (axb)y(czd)  abxcdzy
         * ((axb)yc)zd  abxcydz
         * (ax(byc))zd  abcyxdz
         * ax(by(czd))  abcdzyx
         * ax((byc)zd)  abcydzx
         */
        static void Main(string[] args)
        {
            double[] nums = new double[4] { 5, 5, 5, 1 };
            string x = "", y = "", z = "";
            double a = 0, b = 0, c = 0, d = 0;
            for (int i = 0; i < 4; i++)
            {
                for (int j = 0; j < 4; j++)
                {
                    for (int k = 0; k < 4; k++)
                    {
                        x = i == 0 ? "+" : i == 1 ? "-" : i == 2 ? "*" : "/";
                        y = j == 0 ? "+" : j == 1 ? "-" : j == 2 ? "*" : "/";
                        z = k == 0 ? "+" : k == 1 ? "-" : k == 2 ? "*" : "/";
                        for (int ia = 0; ia < 4; ia++)
                        {
                            a = nums[ia];
                            for (int ib = 0; ib < 4; ib++)
                            {
                                if (ia == ib)
                                {
                                    continue;
                                }
                                b = nums[ib];
                                for (int ic = 0; ic < 4; ic++)
                                {
                                    if (ic == ia || ic == ib)
                                    {
                                        continue;
                                    }
                                    c = nums[ic];
                                    d = nums[6 - ia - ib - ic];
                                    if (Math.Abs(Calc(Calc(a, b, x), Calc(c, d, z), y) - 24d) < 0.01)
                                    {
                                        System.Console.WriteLine("({0}{4}{1}){5}({2}{6}{3}) = 24", a, b, c, d, x, y, z);
                                    }
                                    if (Math.Abs(Calc(Calc(Calc(a, b, x), c, y), d, z) - 24d) < 0.01)
                                    {
                                        System.Console.WriteLine("(({0}{4}{1}){5}{2}){6}{3} = 24", a, b, c, d, x, y, z);
                                    }
                                    if (Math.Abs(Calc(Calc(a, Calc(b, c, y), x), d, z) - 24d) < 0.01)
                                    {
                                        System.Console.WriteLine("({0}{4}({1}{5}{2})){6}{3} = 24", a, b, c, d, x, y, z);
                                    }
                                    if (Math.Abs(Calc(a, Calc(b, Calc(c, d, z), y), x) - 24d) < 0.01)
                                    {
                                        System.Console.WriteLine("{0}{4}({1}{5}({2}{6}{3})) = 24", a, b, c, d, x, y, z);
                                        //System.Console.WriteLine(Math.Abs(Calc(a, Calc(b, Calc(c, d, z), y), x)));
                                    }
                                    if (Math.Abs(Calc(a, Calc(Calc(b, c, y), d, z), x) - 24d) < 0.01)
                                    {
                                        System.Console.WriteLine("{0}{4}(({1}{5}{2}){6}{3}) = 24", a, b, c, d, x, y, z);
                                    }
                                }
                            }
                        }

                    }
                }
            }
        }

        static double Calc(double a, double b, string oper)
        {
            double result = 0;
            switch (oper)
            {
                case "+":
                    result = a + b; break;
                case "-":
                    result = a - b; break;
                case "*":
                    result = a * b; break;
                case "/":
                    result = a / b; break;
                default: result = 0; break;
            }
            return result;
        }
    }
}