NO complete CPT LAB9

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

struct treenode {
    struct treenode *left;
    struct treenode *right;
    int data;
};
typedef struct treenode TREENODE;
typedef TREENODE *TREE;

void insert_node(TREE *tp, int value);
void preorder_print(TREE t);
int is_empty_tree ( TREE t );
int root_value(TREE t);
int main(){
    TREE t = NULL;
    int i = 0, tmp;
    do{
        printf("N%02d: ", i + 1);
        scanf(" %d", &tmp);
        insert_node(&t,tmp);
        i++;
    }while(tmp > 0);
    preorder_print(t);
    return 0;
}
void insert_node(TREE *tp, int value) {
    if (*tp == NULL) {
        printf("tp == null\n");
        *tp = malloc(sizeof(TREENODE));
        (*tp)->data = value;
        (*tp)->left = NULL;
        (*tp)->right = NULL;
    }else if (value < (*tp)->data ){
        printf("tp <<<\n");
        insert_node(&((*tp)->left), value);
    }else if (value > (*tp)->data ){
        printf("tp >>>\n");
        insert_node(&((*tp)->right), value);
    }else{
        printf("duplicate node\n");
    }
}

int is_empty_tree ( TREE t ){
    if (t == NULL) {
        printf("in empty null\n");
        return 1;
    }else{
        printf("NO in empty null\n");
        return 0;
    }
}
int root_value(TREE t){
    if (!is_empty_tree){
        fprintf(stderr, "Tree is empty \n");
        return -1;
    }else{
        return t->data;
    }
}

TREE ls_tree(TREE t){
    return t->left;
}
TREE rs_tree(TREE t){
    return t->right;
}


void preorder_print(TREE t){
    if (!is_empty_tree(t)) {
        printf("%d\n", root_value(t));
        preorder_print(ls_tree(t));
        preorder_print(rs_tree(t));
    }
}