暴力枚举

#include<bits/stdc++.h>
using namespace std;
struct node{
	int root;
	int left;
	int right;
}tree[2000];
void first(int it){
	if(it==0) return;
	cout<<tree[it].root <<" ";
	first(tree[it].left);
	first(tree[it].right );
	
}
void first1(int it){
	if(it==0) return;
	first1(tree[it].left);
	cout<<tree[it].root <<" ";
	first1(tree[it].right );
	
}
void first2(int it){
	if(it==0) return;
	first2(tree[it].left);
	first2(tree[it].right );
	cout<<tree[it].root <<" ";
}
int n,m,cnt=0,sum=0,ans=0,a[1001],temp;
int main(){
	cin>>n;
	for(int i=0;i<n;i++){
		int root;
		cin>>root;
		tree[root].root =root;
		cin>>tree[root].left >>tree[root].right;
	}
	first(1);
	cout<<endl;
	first1(1);
	cout<<endl;
	first2(1);
	return 0;
}