题解

#include<bits/stdc++.h>
using namespace std;

const int maxn = 1e6+9;
struct node{
int left,right;
}tree[109];

void preorder(int x){
cout << x << ' ';
if (tree[x].left)preorder(tree[x].left);
if (tree[x].right) preorder(tree[x].right);
}

void midorder(int x){
if (tree[x].left)midorder(tree[x].left);
cout << x << ' ';
if (tree[x].right) midorder(tree[x].right);
}

void backorder(int x){
if (tree[x].left)backorder(tree[x].left);
if (tree[x].right)backorder(tree[x].right);
cout << x << ' ';
}

int main(){
int n;
cin >> n;
for (int i = 1; i <= n; i++){
int x,l,r;
cin >> x >> l >> r;
tree[x].left = l;
tree[x].right = r;
}preorder(1);
cout << endl;
midorder(1);
cout << endl;
backorder(1);

return 0;

}