100pts TLE 求助

#include <bits/stdc++.h>
using namespace std;
const int maxn = 5e5 + 5;
int father[maxn], head[maxn], head_query[maxn], ans[maxn], cnt_query, cnt;
bool vis[maxn];

struct Edge {
	int to, next, num;
} edge[2 * maxn], query[2 * maxn];

void init() {
	for (int i = 0; i < 2 * maxn; ++i) {
		edge[i].next = -1;
		head[i] = -1;
		query[i].next = -1;
		head_query[i] = -1;
	}
	cnt = 0;
	cnt_query = 0;
}

void add(int u, int v) {
	edge[cnt].to = v;
	edge[cnt].next = head[u];
	head[u] = cnt++;
}

void add_query(int x, int y,int num) {
	query[cnt_query].to = y;
	query[cnt_query].num = num;
	query[cnt_query].next = head_query[x];
	head_query[x] = cnt_query++;
}

int find_set(int x) {
	return father[x] == x ? x : find_set(father[x]);
}

void Tarjan(int x) {
	vis[x] = true;
	for (int i = head[x]; ~i; i = edge[i].next) {
		int y = edge[i].to;
		if (!vis[y]) {
			Tarjan(y);
			father[y] = x;
		}
	}
	for (int i = head_query[x]; ~i; i = query[i].next) {
		int y = query[i].to;
		if (vis[y]) {
			ans[query[i].num] = find_set(y);
		}
	}
}

int main() {
	ios::sync_with_stdio(false);
	cin.tie(nullptr), cout.tie(nullptr);
	init();
	memset(vis, 0, sizeof(vis));
	int n, m, root;
	cin >> n >> m >> root;
	for (int i = 1; i < n; i++) {
		father[i] = i;
		int u, v;
		cin >> u >> v;
		add(u, v);
		add(v, u);
	}
	for (int i = 1; i <= m; i++) {
		int x, y;
		cin >> x >> y;
		add_query(x, y, i);
		add_query(y, x, i);
	}
	Tarjan(root);
	for (int i = 1; i <= m; i++) {
		cout << ans[i] << '\n';
	}
	
	return 0;
}