数据结构中用C#实现“表达式计算”

最近重新翻起以前学的数据结构,原来是用C写的,今天用C#重新回温一下,加深一点印象.

目前还不支持单目操作符,只支持双目的,以后改进吧.:)



using System;
using System.Drawing;
using System.Collections;
using System.ComponentModel;
using System.Windows.Forms;
using System.Data;

namespace Expression1
{
/// <summary>
/// Form1 的摘要说明。
/// </summary>
public class Form1 : System.Windows.Forms.Form
{
private System.Windows.Forms.Label label1;
private System.Windows.Forms.Label label2;
private System.Windows.Forms.TextBox txtInfix;
private System.Windows.Forms.TextBox txtPostfix;
private System.Windows.Forms.Button btnPostfix;
private System.Windows.Forms.Button btnCalc;
private System.Windows.Forms.TextBox txtCalc;
/// <summary>
/// 必需的设计器变量。
/// </summary>
private System.ComponentModel.Container components = null;

public Form1()
{
//
// Windows 窗体设计器支持所必需的
//
InitializeComponent();

//
// TODO: 在 InitializeComponent 调用后添加任何构造函数代码
//
}

/// <summary>
/// 清理所有正在使用的资源。
/// </summary>
protected override void Dispose( bool disposing )
{
if( disposing )
{
if (components != null)
{
components.Dispose();
}
}
base.Dispose( disposing );
}

#region Windows 窗体设计器生成的代码
/// <summary>
/// 设计器支持所需的方法 - 不要使用代码编辑器修改
/// 此方法的内容。
/// </summary>
private void InitializeComponent()
{
this.txtInfix = new System.Windows.Forms.TextBox();
this.txtPostfix = new System.Windows.Forms.TextBox();
this.btnPostfix = new System.Windows.Forms.Button();
this.label1 = new System.Windows.Forms.Label();
this.label2 = new System.Windows.Forms.Label();
this.btnCalc = new System.Windows.Forms.Button();
this.txtCalc = new System.Windows.Forms.TextBox();
this.SuspendLayout();
//
// txtInfix
//
this.txtInfix.Location = new System.Drawing.Point(88, 24);
this.txtInfix.Name = "txtInfix";
this.txtInfix.Size = new System.Drawing.Size(176, 21);
this.txtInfix.TabIndex = 0;
this.txtInfix.Text = "";
//
// txtPostfix
//
this.txtPostfix.Location = new System.Drawing.Point(88, 88);
this.txtPostfix.Name = "txtPostfix";
this.txtPostfix.Size = new System.Drawing.Size(176, 21);
this.txtPostfix.TabIndex = 1;
this.txtPostfix.Text = "";
//
// btnPostfix
//
this.btnPostfix.FlatStyle = System.Windows.Forms.FlatStyle.System;
this.btnPostfix.Location = new System.Drawing.Point(120, 56);
this.btnPostfix.Name = "btnPostfix";
this.btnPostfix.TabIndex = 2;
this.btnPostfix.Text = "转化";
this.btnPostfix.Click += new System.EventHandler(this.btnPostfix_Click);
//
// label1
//
this.label1.Location = new System.Drawing.Point(8, 24);
this.label1.Name = "label1";
this.label1.Size = new System.Drawing.Size(72, 23);
this.label1.TabIndex = 3;
this.label1.Text = "中缀表达式";
this.label1.TextAlign = System.Drawing.ContentAlignment.MiddleCenter;
//
// label2
//
this.label2.Location = new System.Drawing.Point(8, 88);
this.label2.Name = "label2";
this.label2.Size = new System.Drawing.Size(72, 23);
this.label2.TabIndex = 4;
this.label2.Text = "后缀表达式";
this.label2.TextAlign = System.Drawing.ContentAlignment.MiddleCenter;
//
// btnCalc
//
this.btnCalc.FlatStyle = System.Windows.Forms.FlatStyle.System;
this.btnCalc.Location = new System.Drawing.Point(24, 136);
this.btnCalc.Name = "btnCalc";
this.btnCalc.TabIndex = 5;
this.btnCalc.Text = "计算结果";
this.btnCalc.Click += new System.EventHandler(this.btnCalc_Click);
//
// txtCalc
//
this.txtCalc.Location = new System.Drawing.Point(120, 136);
this.txtCalc.Name = "txtCalc";
this.txtCalc.Size = new System.Drawing.Size(144, 21);
this.txtCalc.TabIndex = 6;
this.txtCalc.Text = "";
//
// Form1
//
this.AutoScaleBaseSize = new System.Drawing.Size(6, 14);
this.ClientSize = new System.Drawing.Size(292, 182);
this.Controls.Add(this.txtCalc);
this.Controls.Add(this.btnCalc);
this.Controls.Add(this.label2);
this.Controls.Add(this.label1);
this.Controls.Add(this.btnPostfix);
this.Controls.Add(this.txtPostfix);
this.Controls.Add(this.txtInfix);
this.MaximizeBox = false;
this.Name = "Form1";
this.Text = "表达式计算";
this.ResumeLayout(false);

}
#endregion

/// <summary>
/// 应用程序的主入口点。
/// </summary>
[STAThread]
static void Main()
{
Application.EnableVisualStyles();
Application.DoEvents();
Application.Run(new Form1());
}

private void btnPostfix_Click(object sender, System.EventArgs e)
{
try
{
Calculator calc = new Calculator(this.txtInfix.Text.Replace(" ",""));
this.txtPostfix.Text = calc.PostFix();
}
catch(Expressception ex)
{
MessageBox.Show(ex.Message);
}
}

private void btnCalc_Click(object sender, System.EventArgs e)
{
try
{
Calculator calc = new Calculator(this.txtInfix.Text.Replace(" ",""));
this.txtCalc.Text = calc.Run().ToString();
}
catch(Expressception ex)
{
MessageBox.Show(ex.Message);
}
}
}

public class Calculator
{
private string _expression;
private Stack s;

public Calculator(string expression)
{
this._expression = expression;
s = new Stack();
}

public double Run()
{
string expression=PostFix();
string[] aryString = expression.Split('|');

foreach(string str in aryString)
{
if(IsNumber(str))
{
double d = Convert.ToDouble(str.ToString());
AddOperands(d);
}
else
{
DoOperator(str);
}

}
return (double)s.Pop();
}

private bool IsNumber(string str)
{
if(str.Length>1)
{
return true;
}
else
{
return Char.IsDigit(str[0]);
}
}

private void AddOperands(double val)
{
s.Push(val);
}

private bool Get2Operands(out double left,out double right)
{

try
{
right = (double)s.Pop();
left = (double)s.Pop();
}
catch(InvalidOperationException)
{
right = 0;
left = 0;
return false;
}
return true;
}

private void DoOperator(string op)
{
double left,right;
bool result = Get2Operands(out left,out right);
if(result)
switch(op)
{
case "+": s.Push(left+right); break;
case "-": s.Push(left-right); break;
case "*": s.Push(left*right); break;
case "/":
if(right == 0.0)
{
s.Clear();
//Divide by 0!
throw new Expressception("除数不能为零");

}
else
s.Push(left/right);
break;
case "^":
s.Push(Math.Pow(left,right));
break;
}
else
s.Clear();
}

public string PostFix()
{
string str = this._expression+"#";
char tempc;
char[] chars = str.ToCharArray();
Stack ts = new Stack();
ts.Push('#');
string str1="";
string tmpStr="";
bool isNum = false;
foreach(char c in chars)
{
if(Char.IsDigit(c))
{
tmpStr += c.ToString();
isNum = true;
}
else
{
if(isNum)
{
str1 += tmpStr+"|";
tmpStr = "";
}
isNum=false;
if(c == ')')
{
for(tempc = Convert.ToChar(ts.Pop());tempc!='(';tempc = Convert.ToChar(ts.Pop()))
str1+=tempc.ToString()+"|";
}
else
{
for(tempc = Convert.ToChar(ts.Pop());Isp(tempc)>Icp(c);tempc = Convert.ToChar(ts.Pop()))
str1+=tempc.ToString()+"|";
ts.Push(tempc);
ts.Push(c);
}
}
}
return str1.Substring(0,str1.Length-1);
}

private int Isp(char c)
{
int k;
switch(c)
{
case '#': k=0; break;
case '(': k=1; break;
case '^': k=7; break;
case '*':
case '/':
case '%': k=5; break;
case '+':
case '-': k=3; break;
case ')': k=8; break;
default:
//Unknown operator!
throw new Expressception("不知道的操作符!");
}
return k;
}

private int Icp(char c)
{
int k;
switch(c)
{
case '#': k=0; break;
case '(': k=8; break;
case '^': k=6; break;
case '*':
case '/':
case '%': k=4; break;
case '+':
case '-': k=2; break;
case ')': k=1; break;
default:
//Unknown operator!
throw new Expressception("不知道的操作符!");
}
return k;
}

}

public class Expressception : Exception
{
public Expressception(string msg) : base(msg)
{
}
}