lca 板子题求助

#include <bits/stdc++.h>
using i64 = long long;

void solve() {

	int n;
	std::cin >> n;
	std::vector<std::vector<int>> adj(n);
	for (int i = 1; i < n; ++i) {
		int u, v;
		std::cin >> u >> v;
		--u, --v;
		adj[u].emplace_back(v);
		adj[v].emplace_back(u);
	}
	const int T = std::__lg(n) + 2;
	std::vector<std::vector<int>> fa(n, std::vector<int>(T));
	std::vector<int> d(n);
	{
		auto dfs = [&](auto&& self, int x, int f)->void {
			for (auto& y : adj[x]) {
				if (y == f) continue;
				d[y] = d[x] + 1;
				fa[y][0] = x;
				self(self, y, x);
			}
		};
		dfs(dfs, 0, -1);
	}
	
	{
		std::queue<int> q;
		q.emplace(0);
		std::vector<int> st(n);
		while (q.size()) {
			auto x = q.front();
			q.pop();
			if (st[x]) continue;
			st[x] = 1;
			for (int i = T - 1; i >= 1; --i) {
				fa[x][i] = fa[fa[x][i - 1]][i - 1];
			}
			for (auto& y : adj[x]) {
				q.emplace(y);
			}
		}
	}
	int s, t;
	std::cin >> s >> t;
	--s, --t;
	/*for (int i = 0; i < n; ++i) {
		for (int j = 0; j < T; ++j) {
			std::cout << fa[i][j] << " ";
		}
		std::cout << '\n';
	}*/

	auto lca = [&](int l, int r)->int {
		if (d[l] < d[r]) std::swap(l, r);
		for (int i = T - 1; i >= 0; --i) {
			if (d[fa[l][i]] >= d[r]) {
				l = fa[l][i];
			}
		}
		if (l == r) {
			return l;
		}
		for (int i = T - 1; i >= 0; --i) {
			if (fa[l][i] != fa[r][i]) {
				l = fa[l][i];
				r = fa[r][i];
			}
		}
		return fa[l][0];
	};

	int F = lca(s, t);
	
	int deep = std::ranges::max(d);
	int Lca = 2 * (d[s] - d[F]) + (d[t] - d[F]);
	
	std::vector<int> cnt(deep + 1);

	for (int i = 0; i < n; ++i) {
		++cnt[d[i]];
	}

	std::cout << deep + 1 << "\n" << std::ranges::max(cnt) << "\n" << Lca << '\n';
	
}

int main() {

	int t = 1;
	//std::cin >> t;
	while (t --)
	solve();

	return 0;
}