lab program4

Lab program-4

Design, Develop and Implement a Program in C for converting an Infix Expression to Postfix Expression. Program should support for both parenthesized and free parenthesized expressions with the operators: +, -, *, /, %(Remainder), ^(Power) and alphanumeric operands.

#define SIZE 50 /* Size of Stack */
#include <ctype.h>
#include <stdio.h>
char s[SIZE];
int top = -1; /* Global declarations */

push(char elem) /* Function for PUSH operation */
{
s[++top] = elem;
}

char pop() /* Function for POP operation */
{
return (s[top--]);
}

int pr(char elem) /* Function for precedence */
{
   switch (elem)
   {
       case '#':
           return 0;
       case '(':
           return 1;
       case '+':
       case '-':
           return 2;
       case '*':
       case '/':
       case '%':
           return 3;
       case '^':
               return 4;
   }
}
void main() /* Main Program */
{
char infx[50], pofx[50], ch, elem;
int i = 0, k = 0;
printf("\n\nRead the Infix Expression \n ");
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(); /* Remove ( */
}

else /* Operator */
{
while (pr(s[top]) >= pr(ch))
pofx[k++] = pop();
push(ch);
}
}
while (s[top] != '#') /* Pop from stack till empty */
pofx[k++] = pop();
pofx[k] = '\0'; /* Make pofx as valid string */
printf("\n\nGiven Infix Expn: %s Postfix Expn: %s\n", infx, pofx);
}