计算24点C#代码

C#代码，并修正前门c++代码的一个bug

using System;using System.Collections.Generic;using System.Linq;using System.Text;using System.IO;namespace Calc24Points{    public class Cell    {        public enum Type        {            Number,            Signal        }        public int Number;        public char Signal;        public Type Typ;        public Cell Right;        public Cell Left;        /// <summary>        /// 符号优先级        /// </summary>        public int Priority        {            get            {                if (Typ == Type.Signal)                {                    switch (Signal)                    {                        case '+': return 0;                        case '-': return 0;                        case '*': return 1;                        case '/': return 1;                        default: return -1;                    }                }                return -1;            }        }        /// <summary>        /// 基本单元构造函数        /// </summary>        /// <param name="t">单元类型，数值或符号</param>        /// <param name="num">数值</param>        /// <param name="sig">符号</param>        public Cell(Type t, int num, char sig)        {            Right = null;            Left = null;            Typ = t;            Number = num;            Signal = sig;        }        public Cell()        {            Right = null;            Left = null;            Number = 0;            Typ = Type.Number;        }        public Cell(Cell c)        {            Right = null;            Left = null;            Number = c.Number;            Signal = c.Signal;            Typ = c.Typ;        }    }    public class Calc24Points    {        string m_exp;        bool m_stop;        Cell[] m_cell;        int[] m_express;        StringWriter m_string;        public Calc24Points(int n1, int n2, int n3, int n4)        {            m_cell = new Cell[8];            m_cell[0] = new Cell(Cell.Type.Number, n1, '?');            m_cell[1] = new Cell(Cell.Type.Number, n2, '?');            m_cell[2] = new Cell(Cell.Type.Number, n3, '?');            m_cell[3] = new Cell(Cell.Type.Number, n4, '?');            m_cell[4] = new Cell(Cell.Type.Signal, 0, '+');            m_cell[5] = new Cell(Cell.Type.Signal, 0, '-');            m_cell[6] = new Cell(Cell.Type.Signal, 0, '*');            m_cell[7] = new Cell(Cell.Type.Signal, 0, '/');            m_stop = false;            m_express = new int[7];            m_string = new StringWriter();            m_exp = null;        }        public override string ToString()        {            if (m_exp == null)            {                PutCell(0);                m_exp = m_string.ToString();            }            if (m_exp != "") return m_exp;            return null;        }        /// <summary>        /// 在第n位置放置一个单元        /// </summary>        /// <param name="n"></param>        void PutCell(int n)        {            if (n >= 7)            {                if (Calculate())                {                    m_stop = true;                    Formate();                }                return;            }            int end = 8;            if (n < 2) end = 4;            for (int i = 0; i < end; ++i)            {                m_express[n] = i;                if (CheckCell(n)) PutCell(n + 1);                if (m_stop) break;            }        }        /// <summary>        /// 检查当前放置是否合理        /// </summary>        /// <param name="n"></param>        /// <returns></returns>        bool CheckCell(int n)        {            int nums = 0, sigs = 0;            for (int i = 0; i <= n; ++i)            {                if (m_cell[m_express[i]].Typ == Cell.Type.Number) ++nums;                else ++sigs;            }            if (nums - sigs < 1) return false;            if (m_cell[m_express[n]].Typ == Cell.Type.Number) //数值不能重复，但是符号可以重复            {                for (int i = 0; i < n; ++i) if (m_express[i] == m_express[n]) return false;                        }            if (n == 6)            {                if (nums != 4 || sigs != 3) return false;                if (m_cell[m_express[6]].Typ != Cell.Type.Signal) return false;                return true;            }            return true;        }        /// <summary>        /// 计算表达式是否为24        /// </summary>        /// <returns>返回值true为24，否则不为24</returns>        bool Calculate()        {            double[] dblStack = new double[4];            int indexStack = -1;            for (int i = 0; i < 7; ++i)            {                if (m_cell[m_express[i]].Typ == Cell.Type.Number)                {                    ++indexStack;                    dblStack[indexStack] = m_cell[m_express[i]].Number;                }                else                {                    switch (m_cell[m_express[i]].Signal)                    {                         case '+':                            dblStack[indexStack - 1] = dblStack[indexStack - 1] + dblStack[indexStack];                            break;                        case '-':                            dblStack[indexStack - 1] = dblStack[indexStack - 1]-+ dblStack[indexStack];                            break;                        case '*':                            dblStack[indexStack - 1] = dblStack[indexStack - 1] * dblStack[indexStack];                            break;                        case '/':                            dblStack[indexStack - 1] = dblStack[indexStack - 1] / dblStack[indexStack];                            break;                    }                    --indexStack;                }            }            if (Math.Abs(dblStack[indexStack] - 24) < 0.1) return true;            return false;        }        /// <summary>        /// 后缀表达式到中缀表达式        /// </summary>        void Formate()        {            Cell[] c = new Cell[7];            for (int i = 0; i < 7; ++i) c[i] = new Cell(m_cell[m_express[i]]);            int[] cStack = new int[4];            int indexStack = -1;            for (int i = 0; i < 7; ++i)            {                if (c[i].Typ == Cell.Type.Number)                {                    ++indexStack;                    cStack[indexStack] = i;                }                else                {                    c[i].Right = c[cStack[indexStack]];                    --indexStack;                    c[i].Left = c[cStack[indexStack]];                    cStack[indexStack] = i;                }            }            ToStringFormate(c[cStack[indexStack]]);        }        void ToStringFormate(Cell root)        {            if (root.Left.Typ == Cell.Type.Number)            {                m_string.Write(root.Left.Number);                m_string.Write(root.Signal);            }            else            {                if (root.Priority > root.Left.Priority)                {                    m_string.Write("(");                    ToStringFormate(root.Left);                    m_string.Write(")");                }                else ToStringFormate(root.Left);                m_string.Write(root.Signal);            }            if (root.Right.Typ == Cell.Type.Number) m_string.Write(root.Right.Number);            else            {                if (root.Priority >= root.Right.Priority)                {                    m_string.Write("(");                    ToStringFormate(root.Right);                    m_string.Write(")");                }                else ToStringFormate(root.Right);            }        }    }}