Write a C Program that uses Stack Operations to perform the Converting an infix expression into postfix expression

 

#include <stdio.h>

#include <conio.h>

#include <ctype.h>

#define SIZE 50

char s[SIZE];

int top=-1;

push(char elem)

{

    s[++top]=elem;

}

 

char pop()

{

    return(s[top--]);

}

 

int pr(char elem)

{

    switch(elem)

    {

    case '#': return 0;

    case '(': return 1;

    case '+':

    case '-': return 2;

    case '*':

    case '/': return 3;

    }

}

 

void main()

{

    char infx[50],pofx[50],ch,elem;

    int i=0,k=0;

 

    printf("\n\nRead the Infix Expression ? ");

    scanf("%s",infx);

    push('#');

    while( (ch=infx[i++]) != '\0')

    {

    if( ch == '(') push(ch);

    else

    if(isalnum(ch)) pofx[k++]=ch;

      else

    if( ch == ')')

    {

        while( s[top] != '(')

      pofx[k++]=pop();

        elem=pop();

    }

    else

    {

        while( pr(s[top]) >= pr(ch) )

      pofx[k++]=pop();

        push(ch);

    }

    }

    while( s[top] != '#')

  pofx[k++]=pop();

    pofx[k]='\0';

    printf("\nGiven Infix Expn: %s  \nPostfix Expn: %s\n",infx,pofx);

   

    return 0;

}