infix to postfix.cpp

infix to postfix program,.

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 A C++ Program to convert an Infix Expression into a Postfix Expression.

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  /*************************************************************************

	  By :
		Muhammad Tahir Shahzad  [ MTS ]
		B.C.S Honours  [ 2000-04 ]
		Government College University Lahore
		Pakistan

      E-mail :  [e-mail]

    Web-Site :  www.mts-home.cjb.net  [ www.wol.net.pk/mtshome ]
		www.mtshome.cjb.net   [ www.geocities.com/mtahirshahzad ]

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 //---------------------------  Header Files  ----------------------------//
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 # include <iostream.h>
 # include   <string.h>
 # include   <stdlib.h>
 # include    <conio.h>

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 //--------------------------  Global Variables  -------------------------//
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 int top=-1;

 char Stack[100]={NULL};

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 //------------------------  Function Prototypes  ------------------------//
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 void push(const char);
 const char pop( );

 void infix_to_postfix(const char *);

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 //------------------------------  main( )  ------------------------------//
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 int main( )
    {
       clrscr( );

       char Infix_expression[100]={NULL};

       cout<<"\n\n Enter the Infix Expression : ";
       cin.getline(Infix_expression,80);

       infix_to_postfix(Infix_expression);

       getch( );
       return 0;
    }

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 //------------------------  Function Definitions  -----------------------//
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 /*************************************************************************/
 //-----------------------------  push(const char)  ----------------------//
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 void push(const char Symbol)
    {
       if(top==99)
	  cout<<"Error : Stack is full."<<endl;

       else
	  {
	     top++;
	     Stack[top]=Symbol;
	  }
    }

 /*************************************************************************/
 //--------------------------------  pop( )  -----------------------------//
 /*************************************************************************/

 const char pop( )
    {
       char Symbol=NULL;

       if(top==-1)
	  cout<<"Error : Stack is empty."<<endl;

       else
	  {
	     Symbol=Stack[top];
	     Stack[top]=NULL;
	     top--;
	  }

       return Symbol;
    }

 /*************************************************************************/
 //---------------------  infix_to_postfix(const char *)  ----------------//
 /*************************************************************************/

 void infix_to_postfix(const char *Infix)
    {
       char Infix_expression[100]={NULL};
       char Postfix_expression[100]={NULL};

       strcpy(Infix_expression,"(");
       strcat(Infix_expression,Infix);
       strcat(Infix_expression,")");

       char Symbol[5]={NULL};
       char Temp[5]={NULL};

       for(int count=0;count<strlen(Infix_expression);count++)
	  {
	     Symbol[0]=Infix_expression[count];

	     if(Symbol[0]=='(')
		push(Symbol[0]);

	     else if(Symbol[0]==')')
		{
		   Symbol[0]=pop( );

		   while(Symbol[0]!='(')
		      {
			 strcat(Postfix_expression,Symbol);

			 Symbol[0]=pop( );
		      }
		}

	     else if(Symbol[0]=='^' || Symbol[0]=='*' || Symbol[0]=='/'
				    || Symbol[0]=='+' || Symbol[0]=='-')
		{
		   if(Symbol[0]=='*' || Symbol[0]=='/')
		      {
			 Temp[0]=pop( );

			 while(Temp[0]=='^' || Temp[0]=='*' || Temp[0]=='/')
			    {
			       strcat(Postfix_expression,Temp);

			       Temp[0]=pop( );
			    }

			 push(Temp[0]);
		      }

		   else if(Symbol[0]=='+' || Symbol[0]=='-')
		      {
			 Temp[0]=pop( );

			 while(Temp[0]!='(')
			    {
			       strcat(Postfix_expression,Temp);

			       Temp[0]=pop( );
			    }

			 push(Temp[0]);
		      }

		   push(Symbol[0]);
		}

	     else
		strcat(Postfix_expression,Symbol);
	  }

       cout<<"\n\n Postfix Expression : "<<Postfix_expression<<endl;
    }

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 //-----------------------------  THE END  -------------------------------//
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