#include <stdio.h>
#include <stdlib.h>

typedef struct Node node;
struct Node {
  int id;
  struct Node *left;
  struct Node *right;
};

node *new(int id) {
  node *n = malloc(sizeof(node));
  n->left = n->right = NULL;
  n->id = id;
  return n;
}

void preorder(node *n) {
  if (!n)
    return;

  printf("%d ", n->id);
  preorder(n->left);
  preorder(n->right);
}

void postorder(node *n) {
  if (!n)
    return;

  postorder(n->left);
  postorder(n->right);
  printf("%d ", n->id);
}

void inorder(node *n) {
  if (!n)
    return;

  inorder(n->left);
  printf("%d ", n->id);
  inorder(n->right);
}

void free_tree(node *n) {
  if(!n)
    return;

  free_tree(n->left);
  free_tree(n->right);
  free(n);
}  

int main() {
  node *root = new(1);
  root->left = new(4);
  root->right = new(6);
  root->left->left = new(2);
  root->left->right = new(1783);
  root->left->right->left = new(100);

  printf("Preorder: ");
  preorder(root);
  printf("\n");
  printf("Postorder: ");
  postorder(root);
  printf("\n");
  printf("Inorder: ");
  inorder(root);

  free_tree(root);
}