#include <bits/stdc++.h>

using namespace std;

typedef struct node {
	int data;
	struct node *lchild,*rchild;
} node,*Tree;

void createTree (Tree &T,int x) {
	if(T==NULL){
		T=new node;
		T->data=x;T->lchild=NULL;T->rchild=NULL;//左右孩子的初始化
	}else if(x>T->data) createTree(T->rchild,x);
	else if(x<T->data) createTree(T->lchild,x);
}
void preorder (Tree T) {
	if(T!=NULL){
		cout<<T->data<<" ";
		preorder(T->lchild);
		preorder(T->rchild);
		
	}
}
void inorder (Tree T) {
	if(T!=NULL){
		inorder(T->lchild);
		cout<<T->data<<" ";
		inorder(T->rchild);
		
	}
}
void postorder (Tree T) {
	if(T!=NULL){
		postorder(T->lchild);
		postorder(T->rchild);
		cout<<T->data<<" ";
	}
}

int main() {
	int n,x;
	while(scanf("%d",&n)!=EOF){//while(cin>>n)
		Tree T=NULL; //初始化非常重要，否则报错
		while(n--){
			scanf("%d",&x);
			createTree(T,x);
		}
		...