In Nut Thu K Cua CNPTK

#include "stdafx.h"
#include <stdio.h>
#include <stdio.h>
#include <stdlib.h>
#include <conio.h>

typedef int element_type;
typedef struct node
{
  element_type element;
  struct node *left, *right;
} NODE;

NODE *root;

void khoi_tao_cay(NODE ** root)
{
  *root = NULL;
}

void insert(NODE *tmp, NODE **root)
{

  if (tmp->element < (*root)->element)
    if ((*root)->left)
      insert(tmp, &(*root)->left);
    else
       (*root)->left = tmp;
  else
    if ((*root)->right)
      insert(tmp, &(*root)->right);
    else
       (*root)->right = tmp;
}

void insert_node(element_type e, NODE **root)
{
   NODE *tmp;

   tmp = (NODE *)malloc(sizeof(NODE));
   tmp->element = e;
   tmp->left = NULL;
   tmp->right = NULL;
   if (*root == NULL)
     *root = tmp;
   else
     insert(tmp, root);
}

void nhap_cay(NODE **root)
{
  element_type e;
  printf("\n NHAP CAY NHI PHAN ! \n");
  printf("\n Nhap -1 de ket thuc !\n ");
  int i=1;
  do {

    printf("\n Nhap phan tu thu %d :",i);
    scanf("%d", &e);
    if (e != -1)
      insert_node(e, root);
 i++;
  } while (e != -1);
}

void tim_xuat_nguoc(NODE *root, int x)
{
if(!root)
printf("\n Cay rong !");
else
if(root->element==x)
printf(" %d",root->element);
else
if(root->element>x)
{
tim_xuat_nguoc(root->left,x);
printf(" %d", root->element);
}
else
{
tim_xuat_nguoc(root->right,x);
printf(" %d", root->element);
}
}

void in_nut_thu_k(NODE *root, int k)
{
if(!root)
return;
if(k==0)
{
printf(" %d", root->element);
}
in_nut_thu_k(root->left,k-1);
in_nut_thu_k(root->right, k-1);
}

void in_nut_thu_k(NODE *root, int k);
void duyet_theo_mut(NODE *root, int x)
{
for(int k=x;k>=1;k--)
in_nut_thu_k(root,k);
}

void main()
{
   khoi_tao_cay(&root);
   nhap_cay(&root);
   // xuat cac phan tu , tu phan tu =x ve goc
   int x;
   printf("\n Nhap gia tri xuat nguoc :");
   scanf("%d",&x);
   tim_xuat_nguoc(root,x);

   int h; // do cao
   printf("\n Nhap mut can in:");
   scanf("%d",&h);
   printf("\n Gia tri cac nut o do cao %d:", h);
   in_nut_thu_k(root,h);

   // xuat cac phan tu tu do cao h ve goc
   printf("\n Xuat cac phan tu tu do cao %d ve goc :",h);
   duyet_theo_mut(root, h);

   getch();
}