#include <stdlib.h> 
struct Tree {
  int val; 
  struct Tree * left; 
  struct Tree * right;
}; 

void free_tree_1(struct Tree * t) {
  if(t == NULL) 
	return;
  free(t);
} 

void free_tree_2(struct Tree * t) {
  if(t == NULL) 
	return;
  free(t); 
  free_tree_2(t->left); 
  free_tree_2(t->right);
} 

void free_tree_3(struct Tree * t) {
  if(t == NULL) 
	return;
  free_tree_3(t->left); 
  free_tree_3(t->right); 
  free(t);
}