Bulls and Cows Solver

PermutationAndCombination.cs

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

namespace _4DigitalSolver
{
    public class PermutationAndCombination<T>
    {
        /// <summary>
        /// 交换两个变量
        /// </summary>
        /// <param name="a">变量1</param>
        /// <param name="b">变量2</param>
        public static void Swap(ref T a, ref T b)
        {
            T temp = a;
            a = b;
            b = temp;
        }

        /// <summary>
        /// 递归算法求数组的组合(私有成员)
        /// </summary>
        /// <param name="list">返回的范型</param>
        /// <param name="t">所求数组</param>
        /// <param name="n">辅助变量</param>
        /// <param name="m">辅助变量</param>
        /// <param name="b">辅助数组</param>
        /// <param name="M">辅助变量M</param>
        private static void GetCombination(ref List<T[]> list, T[] t, int n, int m, int[] b, int M)
        {
            for (int i = n; i >= m; i--)
            {
                b[m - 1] = i - 1;
                if (m > 1)
                {
                    GetCombination(ref list, t, i - 1, m - 1, b, M);
                }
                else
                {
                    if (list == null)
                    {
                        list = new List<T[]>();
                    }
                    T[] temp = new T[M];
                    for (int j = 0; j < b.Length; j++)
                    {
                        temp[j] = t[b[j]];
                    }
                    list.Add(temp);
                }
            }
        }

        /// <summary>
        /// 递归算法求排列(私有成员)
        /// </summary>
        /// <param name="list">返回的列表</param>
        /// <param name="t">所求数组</param>
        /// <param name="startIndex">起始标号</param>
        /// <param name="endIndex">结束标号</param>
        private static void GetPermutation(ref List<T[]> list, T[] t, int startIndex, int endIndex)
        {
            if (startIndex == endIndex)
            {
                if (list == null)
                {
                    list = new List<T[]>();
                }
                T[] temp = new T[t.Length];
                t.CopyTo(temp, 0);
                list.Add(temp);
            }
            else
            {
                for (int i = startIndex; i <= endIndex; i++)
                {
                    Swap(ref t[startIndex], ref t[i]);
                    GetPermutation(ref list, t, startIndex + 1, endIndex);
                    Swap(ref t[startIndex], ref t[i]);
                }
            }
        }

        /// <summary>
        /// 求从起始标号到结束标号的排列，其余元素不变
        /// </summary>
        /// <param name="t">所求数组</param>
        /// <param name="startIndex">起始标号</param>
        /// <param name="endIndex">结束标号</param>
        /// <returns>从起始标号到结束标号排列的范型</returns>
        public static List<T[]> GetPermutation(T[] t, int startIndex, int endIndex)
        {
            if (startIndex < 0 || endIndex > t.Length - 1)
            {
                return null;
            }
            List<T[]> list = new List<T[]>();
            GetPermutation(ref list, t, startIndex, endIndex);
            return list;
        }

        /// <summary>
        /// 返回数组所有元素的全排列
        /// </summary>
        /// <param name="t">所求数组</param>
        /// <returns>全排列的范型</returns>
        public static List<T[]> GetPermutation(T[] t)
        {
            return GetPermutation(t, 0, t.Length - 1);
        }

        /// <summary>
        /// 求数组中n个元素的排列
        /// </summary>
        /// <param name="t">所求数组</param>
        /// <param name="n">元素个数</param>
        /// <returns>数组中n个元素的排列</returns>
        public static List<T[]> GetPermutation(T[] t, int n)
        {
            if (n > t.Length)
            {
                return null;
            }
            List<T[]> list = new List<T[]>();
            List<T[]> c = GetCombination(t, n);
            for (int i = 0; i < c.Count; i++)
            {
                List<T[]> l = new List<T[]>();
                GetPermutation(ref l, c[i], 0, n - 1);
                list.AddRange(l);
            }
            return list;
        }


        /// <summary>
        /// 求数组中n个元素的组合
        /// </summary>
        /// <param name="t">所求数组</param>
        /// <param name="n">元素个数</param>
        /// <returns>数组中n个元素的组合的范型</returns>
        public static List<T[]> GetCombination(T[] t, int n)
        {
            if (t.Length < n)
            {
                return null;
            }
            int[] temp = new int[n];
            List<T[]> list = new List<T[]>();
            GetCombination(ref list, t, t.Length, n, temp, n);
            return list;
        }
    }
}

Program.cs

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

namespace _4DigitalSolver
{
    class Program
    {
        static void Main(string[] args)
        {
            Solver s = new Solver(4);
            while(s.Answers.Count > 1)
            {
                string i, a, b;
                Console.Write("Input=");
                i = Console.ReadLine();
                Console.Write("A=");
                a = Console.ReadLine();
                Console.Write("B=");
                b = Console.ReadLine();
                try
                {
                    s.Filter(new Solver.Guess(i, int.Parse(a), int.Parse(b)));
                }
                catch (Exception e) { }

                Console.WriteLine("{0} remaining: {1}", s.Answers.Count, String.Join(", ", new List<string>(s.Answers).ToArray()));
            }
            Console.ReadKey();
        }
    }
}

Solver.cs

using System;
using System.Collections.Generic;
using System.Text;
using System.Text.RegularExpressions;

namespace _4DigitalSolver
{
    class Solver
    {
        public struct Guess
	    {
            static Regex Duplicate = new Regex(@"(.).*\1");

		    public string Value;
            public int A; public int B;

            public Guess(string value, int a, int b) { Value = value; A = a; B = b; }
            public Guess(string Answer, string Input)
            {
                if (Answer.Length != Input.Length) throw new ArgumentException("Misalign");

                Value = Input;
                if (Answer == Input)
                {
                    A = Value.Length;
                    B = 0;
                    return;
                }

                if (Duplicate.Match(Input).Success) throw new ArgumentException("Dup");

                A = 0; B = 0;
                for (int i = 0; i < Answer.Length; i++)
                {
                    int p = Answer.IndexOf(Input[i]);
                    if (p == i) A++;
                    else if (p != -1) B++;
                }
            }
	    }
        List<string> answers;
        List<Guess> guesses = new List<Guess>();
        int length;

        public Solver(): this(4) {}
        public Solver(int length)
        {
            this.length = length;
            InitAnswer();
        }

        private void InitAnswer() {
            answers = new List<string>();

            var comb = new List<int[]>(PermutationAndCombination<int>.GetCombination(new int[] { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 }, length));
            foreach(var c in comb) {
                var p = PermutationAndCombination<int>.GetPermutation(c);
                answers.AddRange(p.ConvertAll((i) => string.Join("", Array.ConvertAll(i, (j) => j.ToString()))));
            }
        }

        public void Filter(Guess guess)
        {
            guesses.Add(guess);

            answers.RemoveAll((string ans) =>
            {
                if (ans == guess.Value) return true;
                Guess g = new Guess(guess.Value, ans);
                return !(g.A == guess.A && g.B == guess.B);
            });
        }

        public System.Collections.ObjectModel.ReadOnlyCollection<string> Answers { get { return answers.AsReadOnly(); } }
    }
}