Infix to Postfix conversion

GXTechno Tags: c, data, structure, infix, postfix, stack

/*takes an infix expression and converts it into an equivalent postfix expression*/
#include<conio.h>
#include<stdio.h>
#include<string.h>
char stack[50];
int top=-1;
void in_to_post(char infix[]);
void push (char);
char pop();
void main()
{
char infx[25];
printf("Enter the infix expression");
gets(infx);
in_to_post(infx);
getch();
}
void push (char symb)
{
if (top>=49)
{
printf("stack overflow");
getch();
return;
}
else
{
top=top+1;
stack[top]=symb;
}
}
char pop()
{
char item;
if(top==-1)
{
printf("stack empty");
getch();
return(0);
}
else
{
item=stack[top];
top--;
}
return(item);
}
int preced(char ch)
{
if(ch==47)
{
return(5);
}
else
if(ch==42)
{
return(4);
}
else if(ch==43)
{
return(3);
}
else
return(2);
}
void in_to_post(char infix[])
{
int length;
static int index=0,pos=0;
char symbol,temp;
char postfix[40];
length=strlen(infix);
push('#');
while(index<length)
{
symbol=infix[index];
switch(symbol)
{
case'(':push(symbol);
break;
case')' :temp=pop();
while(temp!='(')
{
postfix[pos]=temp;
pos++;
temp=pop();
}
break;
case '+' :
case '-' :
case '*' :
case '/' :
case '^' :
while (preced(stack[top])>=preced(symbol))
{
temp=pop();
postfix[pos]=temp;
pos++;
}
push(symbol);
break;
default : postfix[pos++]=symbol;
break;
}
index++;
}
while(top>0)
{
temp=pop();
postfix[pos++]=temp;
}
postfix[pos++]='\0';
puts(postfix);
return;
}

/*output of the program*/
eneter the infix expression1+2
12+