Table of Content

Program : 

• This Program Accepts Operators : +,-,/,*,(,)
• Sample Infix Expression : (a+b)*c/(a+b*c)

#include<stdio.h>
#include<conio.h>
#include<ctype.h>
#define MAX 100

typedef struct stack
{
 int data[MAX];
 int top;
}stack;

int priority(char);
void init(stack *);
int empty(stack *);
int full(stack *);
char pop(stack *);
void push(stack *,char);
char top(stack *);

void main()
{
stack s;
char x;
int token;
init(&s);
clrscr();
printf("nEnter infix expression:");
  while((token=getchar())!='n')
  {
    if(isalnum(token))
       printf("%c",token);
    else
       if(token == '(')
           push(&s,'(');
       else
       {
         if(token == ')')
             while((x=pop(&s))!='(')
             printf("%c",x);
         else
         {
         while(priority(token)< =priority(top(&s)) && !empty(&s))
             {
             x=pop(&s);
             printf("%c",x);
             }
         push(&s,token);
         }
       }
  }
  while(!empty(&s))
    {
    x=pop(&s);
    printf("%c",x);
    }
getch();
}
//---------------------------------------------
int priority(char x)
{
   if(x == '(')
 return(0);
   if(x == '+' || x == '-')
 return(1);
   if(x == '*' || x == '/' || x == '%')
 return(2);
   return(3);
}
//---------------------------------------------
void init(stack *s)
{
   s->top=-1;
}
//---------------------------------------------
int empty(stack *s)
{
    if(s->top==-1)
 return(1);
    else 
 return(0);
}
//---------------------------------------------
int full(stack *s)
{
    if(s->top==MAX-1)
 return(1);
    else 
 return(0);
}
//---------------------------------------------
void push(stack *s,char x)
{
  s->top=s->top+1;
  s->data[s->top]=x;
}
//---------------------------------------------
char pop(stack *s)
{
   int x;
   x=s->data[s->top];
   s->top=s->top-1;
   return(x);
}
//---------------------------------------------
char top(stack * s)
{
   return(s->data[s->top]);
}
//---------------------------------------------

Explanation : 

while((token=getchar())!='n')

Accepts Expression Character by Character Till Entered Character is ‘n’
After Accepting Single Character do all actions inside while loop.

if(isalnum(token))
 printf("%c",token);

isalnum(token)   checks whether entered Character is Alphabetic or Numeric .
If Entered Character is alpha-numeric then Directly Display it - for more help [Algo] + [Example]
If Entered Character is Opening Bracket then Push Element Onto Stack


if(token == '(')
     push(&s,'(');

If Entered Character is ‘Closing Bracket’ then Pop All Elements till Equivalent Opening Bracket is poped.

if(token == ')')
     while((x=pop(&s))!='(')
  printf("%c",x);

If Entered Character is Operator then - do

else
   {
   while(priority(token)< =priority(top(&s)) && !empty(&s))
     {
     x=pop(&s);
     printf("%c",x);
     }
   push(&s,token);
   }




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