#include<stdio.h>
#include<stdlib.h>
#define MAX_SIZE 100
struct Node
{
  int data;
  struct Node *left, *right;
};

struct Stack
{
  int size;
  int top;
  struct Node **array;
};

struct Node *newNode (int data)
{
  struct Node *node = (struct Node *) malloc (sizeof (struct Node));
  node->data = data;
  node->left = node->right = NULL;
  return node;
}

struct Stack *createStack (int size)
{
  struct Stack *stack = (struct Stack *) malloc (sizeof (struct Stack));
  stack->size = size;
  stack->top = -1;
  stack->array =
    (struct Node **) malloc (stack->size * sizeof (struct Node *));
  return stack;
}

int isFull (struct Stack *stack)
{
  return stack->top - 1 == stack->size;
}

int isEmpty (struct Stack *stack)
{
  return stack->top == -1;
}

void push (struct Stack *stack, struct Node *node)
{
  if (isFull (stack))
    return;
  stack->array[++stack->top] = node;
}

struct Node *pop (struct Stack *stack)
{
  if (isEmpty (stack))
    return NULL;
  return stack->array[stack->top--];
}

struct Node *peek (struct Stack *stack)
{
  if (isEmpty (stack))
    return NULL;
  return stack->array[stack->top];
}

void postorder (struct Node *root)
{
  if (root == NULL)
    return;

  struct Stack *stack = createStack (MAX_SIZE);
  do
    {
      while (root)
    {
      if (root->right)
        push (stack, root->right);
      push (stack, root);

      root = root->left;
    }

      root = pop (stack);

      if (root->right && peek (stack) == root->right)
    {
      pop (stack);
      push (stack, root);
      root = root->right;

    }
      else
    {
      printf ("%d ", root->data);
      root = NULL;
    }
    }
  while (!isEmpty (stack));
}

int main ()
{

  struct Node *root = NULL;
  root = newNode (10);
  root->left = newNode (20);
  root->right = newNode (30);
  root->left->left = newNode (40);
  root->left->right = newNode (50);
  root->right->left = newNode (60);
  root->right->right = newNode (70);
  printf ("Post order traversal of binary tree is :\n");
  printf ("[");
  postorder(root);
  printf ("]");

  return 0;
}