字符串表达式计算C#程序设计

      在编程应用程序过程中，有时需要字符串表达式的值。如字符串："23+56/(102-100)*((36-24)/(8-6))"，结果=191。
      根据数据结构栈的应用介绍，通过把表达式由中序式转换成后序式，再用栈来进行计算。如上述字符串表达式："23+56/(102-100)*((36-24)/(8-6))"，转换为后序时为："23|56|102|100|-|/|*|36|24|-|8|6|-|/|*|+"(其中字符"|"为分隔符)。
      本程序代码如下：在Visual .net 2003 +winXP下编译通过。

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

namespace stringExpressionCalculate
{
 /// <summary>
 /// Form1 的摘要说明。
 /// </summary>
 public class Form1 : System.Windows.Forms.Form
 {

  private System.Windows.Forms.TextBox textBox1;
  private System.Windows.Forms.Button button1;
  private System.Windows.Forms.TextBox textBox2;
  private System.Windows.Forms.Label label1;
  private System.Windows.Forms.Label label2;
 
  /// <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.textBox1 = new System.Windows.Forms.TextBox();
   this.button1 = new System.Windows.Forms.Button();
   this.textBox2 = new System.Windows.Forms.TextBox();
   this.label1 = new System.Windows.Forms.Label();
   this.label2 = new System.Windows.Forms.Label();
   this.SuspendLayout();
   //
   // textBox1
   //
   this.textBox1.Location = new System.Drawing.Point(114, 33);
   this.textBox1.Name = "textBox1";
   this.textBox1.Size = new System.Drawing.Size(273, 21);
   this.textBox1.TabIndex = 0;
   this.textBox1.Text = "23+56/(102-100)*((36-24)/(8-6))";
   //
   // button1
   //
   this.button1.Location = new System.Drawing.Point(180, 144);
   this.button1.Name = "button1";
   this.button1.Size = new System.Drawing.Size(84, 27);
   this.button1.TabIndex = 1;
   this.button1.Text = "计算(&C)";
   this.button1.Click += new System.EventHandler(this.button1_Click);
   //
   // textBox2
   //
   this.textBox2.Location = new System.Drawing.Point(114, 72);
   this.textBox2.Name = "textBox2";
   this.textBox2.Size = new System.Drawing.Size(273, 21);
   this.textBox2.TabIndex = 2;
   this.textBox2.Text = "";
   //
   // label1
   //
   this.label1.AutoSize = true;
   this.label1.Location = new System.Drawing.Point(48, 36);
   this.label1.Name = "label1";
   this.label1.Size = new System.Drawing.Size(54, 17);
   this.label1.TabIndex = 3;
   this.label1.Text = "字符串：";
   //
   // label2
   //
   this.label2.AutoSize = true;
   this.label2.Location = new System.Drawing.Point(39, 75);
   this.label2.Name = "label2";
   this.label2.Size = new System.Drawing.Size(66, 17);
   this.label2.TabIndex = 3;
   this.label2.Text = "计算结果：";
   //
   // Form1
   //
   this.AutoScaleBaseSize = new System.Drawing.Size(6, 14);
   this.ClientSize = new System.Drawing.Size(442, 221);
   this.Controls.Add(this.label1);
   this.Controls.Add(this.textBox2);
   this.Controls.Add(this.button1);
   this.Controls.Add(this.textBox1);
   this.Controls.Add(this.label2);
   this.Name = "Form1";
   this.Text = "Form1";
   this.ResumeLayout(false);

  }
  #endregion

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

  private void button1_Click(object sender, System.EventArgs e)
  {

         textBox2.Text = CalculateParenthesesExpression(textBox1.Text.ToString());
  }

  
  //中序转换成后序表达式再计算
  // 如：23+56/(102-100)*((36-24)/(8-6))
  // 转换成：23|56|102|100|-|/|*|36|24|-|8|6|-|/|*|+"
  //以便利用栈的方式都进行计算。
  private string  CalculateParenthesesExpression(string Expression)
  {
   ArrayList operatorList = new ArrayList();
   string operator1;
   string ExpressionString = "";
   string operand3;
   Expression = Expression.Replace(" ","");
   while(Expression.Length > 0)
   {
    operand3 = "";
    //取数字处理
    if(Char.IsNumber(Expression[0]))
    {
     while(Char.IsNumber(Expression[0]))
     {
      operand3 += Expression[0].ToString() ;
      Expression = Expression.Substring(1);
      if(Expression == "")break;

     }
     ExpressionString += operand3 + "|";
    }

    //取“C”处理
    if(Expression.Length >0 && Expression[0].ToString() == "(")
    {
     operatorList.Add("("); 
     Expression = Expression.Substring(1);
    }

    //取“)”处理
    operand3 = "";
    if(Expression.Length >0 && Expression[0].ToString() == ")")
    {
     do
     {
      
      if(operatorList[operatorList.Count -1].ToString() != "(")
      {
       operand3 += operatorList[operatorList.Count -1].ToString() + "|" ;
       operatorList.RemoveAt(operatorList.Count - 1) ;
      }
      else
      {
       operatorList.RemoveAt(operatorList.Count - 1) ;
       break;
      }
      
     }while(true);
     ExpressionString += operand3;
     Expression = Expression.Substring(1);
    }

    //取运算符号处理
    operand3 = "";
    if(Expression.Length >0 &&  (Expression[0].ToString() == "*" || Expression[0].ToString() == "/" || Expression[0].ToString() == "+" || Expression[0].ToString() == "-"))
    {
     operator1 = Expression[0].ToString();
     if(operatorList.Count>0)
     {
       
      if(operatorList[operatorList.Count -1].ToString() == "(" || verifyOperatorPriority(operator1,operatorList[operatorList.Count - 1].ToString()))
       
       {
        operatorList.Add(operator1);
       }
       else 
       {
        operand3 += operatorList[operatorList.Count - 1].ToString() + "|";
        operatorList.RemoveAt(operatorList.Count - 1);
        operatorList.Add(operator1);
        ExpressionString += operand3 ;
       
       }
      
     }
     else
     {
      operatorList.Add(operator1);
     }
     Expression = Expression.Substring(1);
    }
   }

   operand3 = "";
   while(operatorList.Count != 0)
   {
    operand3 += operatorList[operatorList.Count -1].ToString () + "|";
    operatorList.RemoveAt(operatorList.Count -1);
   } 

   ExpressionString += operand3.Substring(0, operand3.Length -1);  ;
   

   return CalculateParenthesesExpressionEx(ExpressionString);

  }

  // 第二步:把转换成后序表达的式子计算
  //23|56|102|100|-|/|*|36|24|-|8|6|-|/|*|+"
  private string  CalculateParenthesesExpressionEx(string Expression)
  {
   //定义两个栈
   ArrayList operandList =new ArrayList();
   float operand1;
   float operand2;
   string[] operand3;
  
   Expression = Expression.Replace(" ","");
   operand3 = Expression.Split(Convert.ToChar("|"));
 
   for(int i = 0;i < operand3.Length;i++)
   {
    if(Char.IsNumber(operand3[i],0))
    {
     operandList.Add( operand3[i].ToString());
    }
    else
    {
      //两个操作数退栈和一个操作符退栈计算
     operand2 =(float)Convert.ToDouble(operandList[operandList.Count-1]);
     operandList.RemoveAt(operandList.Count-1); 
     operand1 =(float)Convert.ToDouble(operandList[operandList.Count-1]);
     operandList.RemoveAt(operandList.Count-1);
     operandList.Add(calculate(operand1,operand2,operand3[i]).ToString()) ;
    }
    
   }

   return operandList[0].ToString();
  }

 

  //判断两个运算符优先级别
  private bool verifyOperatorPriority(string Operator1,string Operator2)
  {
   
   if(Operator1=="*" && Operator2 =="+")
    return true;
   else if(Operator1=="*" && Operator2 =="-")
    return true;
   else if(Operator1=="/" && Operator2 =="+")
    return true;
   else if(Operator1=="/" && Operator2 =="-")
    return true;
   else
    return false;
  }

  //计算
  private float calculate(float operand1, float operand2,string operator2)
  {
   switch(operator2)
   {
    case "*":
     operand1 *=  operand2;
     break;
    case "/":
     operand1 /=  operand2;
     break;
    case "+":
     operand1 +=  operand2;
     break;
    case "-":
     operand1 -=  operand2;
     break;
    default:
     break;
   }
   return operand1;
  }
 
 }
}

本文地址：http://com.8s8s.com/it/it42078.htm