Binary Tree implementation in c

.c

#include <stdio.h>
#include <stdlib.h>
typedef struct tree
{
    int data;
    struct tree *left;
    struct tree *right;
} tree_node;
tree_node *create(int data, tree_node *left, tree_node *right)
{
    tree_node *node = malloc(sizeof(tree_node));
    node->data = data;
    node->left = left;
    node->right = right;
    return node;
}
void print(tree_node *root)
{
    if (root == NULL)
    {
        return;
    }
    printf("%d ", root->data);
    print(root->left);
    print(root->right);
}
void add(tree_node **root, int data)
{
    tree_node *new_node = create(data, NULL, NULL);
    if (!(*root))
    {
        (*root) = new_node;
        return;
    }
    else if (data <= (*root)->data)
    {
        add(&(*root)->left, data);
    }
    else
    {
        add(&(*root)->right, data);
    }
}
_Bool search(tree_node *root, int data)
{
    _Bool retval;
    if (root == NULL)
    {
        return 0;
    }
    if (root->data == data)
    {
        return 1;
    }
    else
    {
        if (root->data >= data)
        {
            retval = search(root->left, data);
        }
        else
        {
            retval = search(root->right, data);
        }
    }
    return retval;
}
tree_node *min(tree_node *root)
{
    if (!root)
    {
        printf("Tree is empty");
        exit(1);
    }
    tree_node *ret_val;
    if (root->left == NULL)
    {
        ret_val = root;
    }
    else
    {
        ret_val = min(root->left);
    }
    return ret_val;
}
tree_node *max(tree_node *root)
{
    if (!root)
    {
        printf("Tree is empty");
        exit(1);
    }
    tree_node *ret_val;
    if (root->right == NULL)
    {
        ret_val = root;
    }
    else
    {
        ret_val = max(root->right);
    }
    return ret_val;
}
void main()
{
    tree_node *root = NULL;
    add(&root, 15);
    add(&root, 10);
    add(&root, 20);
    add(&root, 25);
    add(&root, 8);
    add(&root, 12);
    add(&root, 50);
    tree_node *min_el = min(root);
    tree_node *max_el = max(root);
    // print(root);
    printf("%d %d", min_el->data, max_el->data);
}