Prefix - Postfix.c

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#define MAX 20
char str[MAX], stack[MAX];
int top = -1;
void push(char c) // to push the character in to the stack
{
   stack[++top] = c;
}
char pop()
{
   return stack[top--];
}
void pre_post() // function to convert prefix to postfix
{
   int n, i, j = 0;
   char c[20];
   char a;
   printf("Enter the prefix expression\n");
   gets(str); // used to scan the prefix expression
   n = strlen(str);
   for (i = 0; i < MAX; i++)
      stack[i] = '\0';
   printf("Postfix expression is:\t");
   for (i = 0; i < n; i++)
   {
      if (str[i] == '+' || str[i] == '-' || str[i] == '*' || str[i] == '/')
      {
         push(str[i]);
      }
      else
      {
         c[j++] = str[i];
         while ((top != -1) && (stack[top] == '#'))
         {
            a = pop();
            c[j++] = pop();
         }
         push('#');
      }
   }
   c[j] = '\0';
   printf("%s", c);
}
int main()
{
   pre_post();
   return 0;
}