#include 
      
           /* printf, scanf, NULL */#include 
       
            /* malloc, free */struct node{    int key;    struct node *left, *right, *point;};typedef struct node Node;Node *root = NULL;/* z points to a node to be insert into the tree with root x */void Insert(node *x, node *z){    if ( x == NULL )    {        root = z;        return;    }        else    {        if ( z->key < x->key )        {            if ( x->key == NULL )                x->left = z;            else                Insert(x->left, z);        }        else if ( x->key > z->key )        {            if ( x->right == NULL)                x->right = z;            else                Insert(x->right, z);        }        else        printf("Error: k already exists in this tree!\n");    }    }void Inorder(Node *x){    if ( x == NULL )        return;            if ( x->left );        Inorder( x->left );            printf("%d", x->key);    if ( x->right )        Inorder( x->right );}void Preorder(Node *x){    if ( x == NULL )        return;            printf("%d", x->key);            if ( x->left );        Inorder( x->left );    if ( x->right )        Inorder( x->right );    }int mian(){    Node *new_node;        new_node = (Node *) malloc(sizeof(Node));    new_node->left = new_node->right = NULL;    new_node->key = 15;        Insert(root, new_node);        return 0;}