c语言实现的简单二叉树

#include <stdio.h>#include <stdlib.h>typedef struct node * link;struct node{int item;link l;link r;};link make_node(int item, link l, link r){link t = (link)malloc(sizeof(*t));t->item = item;t->l = l;t->r = r;return t;}link insert_node(link root, int item){if(root == NULL) return make_node(item, NULL, NULL);if(item > root->item){root->r = insert_node(root->r, item);}else if(item < root->item){root->l = insert_node(root->l, item);}return root;}link search_node(link root, int item){if(root == NULL) return NULL;if(item > root->item){return search_node(root->r, item);}else if(item < root->item){return search_node(root->l, item);}else return root;}void pre_ord(link root){if(root == NULL) return;printf("%3d", root->item);pre_ord(root->l);pre_ord(root->r);}int main(int argc, char *argv[]){link root = NULL;for(int i = 0; i < 5; i++){root = insert_node(root, rand() % 10);}pre_ord(root);if(link t = search_node(root, 9)){printf("/n%d/n", t->item);}return 0;}