Implement a program in c to convert infix notation to postfix notation using stack.

Infix to Postfix Conversion in C

#include stdio.h
#include ctype.h
#include string.h

char stack[100];
int top = -1;

void push(char x)
{
  top++;
  stack[top] = x;
}

char pop()
{
  if(top==-1)
    return -1;
  else
    return stack[top--];
}

int priority(char p)
{
  if (p == '(')
    return 0;
  else if (p == '/' || p == '*')
    return 2;
  else if (p == '+' || p == '-')
    return 1;
  else
    return 0;
}

void main()
{
  int i=0;
  char exp[100];
  printf("\nEnter infix-equation\n");
  scanf("%s", exp);
  printf("\nPost-fix equation:\n");
  while (exp[i] != '\0')
  {
    if (exp[i] == '(')
    {
      push(exp[i]);
    }
    else if (isalnum(exp[i]))
    {
      printf("%c", exp[i]);
    }
    else if (exp[i] == ')')
    {
      char d;
      while (d=pop() != '(')
      {
        printf("%c", d);
      }
    }
    else
    {
      while (priority(stack[top] >= priority(exp[i])))
      {
        printf("%c", pop());
      }
      push(exp[i]);
    }
    i++;
  }
  while (top != -1)
  {
    printf("%c", pop());
  }
}