题解

#include <bits/stdc++.h>
using namespace std;
struct node {
	int left, right;
} t[1010];
void preorder(int root) {
	if (root == 0)
		return;
	cout << root << " ";
	preorder(t[root].left);
	preorder(t[root].right);
}
void inorder(int root) {
	if (root == 0)
		return;
	inorder(t[root].left);
	cout << root << " ";
	inorder(t[root].right);
}
void postorder(int root) {
	if (root == 0)
		return;
	postorder (t[root].left);
	postorder (t[root].right);
	cout << root << " ";
}
int main() {
	int n;
	cin >> n;
	for (int i = 1; i <= n; i++) {
		int idx, left, right;
		cin >> idx >> left >> right;
		t[idx].left = left, t[idx].right = right;
	}
	int root = 1;
	preorder(root);
	cout << endl;
	inorder(root);
	cout << endl;
	postorder(root);
	return 0;
}