二叉树的递归插入，中序遍历

#include "stdio.h"struct node {int key;node* left;node* right;node(int value):left(NULL),right(NULL),key(value){}};void print_tree(node* root){if (root==NULL) {return;}print_tree(root->left);printf("%d ",root->key);print_tree(root->right);}node* insert_tree(node* root,int value){if (root==NULL) {root=new node(value);}else if (root->key>value) {root->left=insert_tree(root->left,value);}else {root->right=insert_tree(root->right,value);}return root;}void main(){node* root = NULL;  int data[10] = {3,2,1,4,6,8,7,10,9,33};  for(int i=0;i<10;i++){  root = insert_tree(root,data[i]);  }  print_tree(root);  }