Language: C++

#include <cstdio>
#include <cmath>
#include <iostream>
#include <sstream>
#include <string>
#include <vector>
#include <map>
#include <queue>
#include <algorithm>

#ifdef _DEBUG
#define DMP(x) cerr << #x << ": " << x << "\n"
#else
#define DMP(x) ((void)0)
#endif

const int MOD = 1000000007, INF = 1111111111; 
using namespace std;
using lint = long long;

template<class T = lint>
struct Edge {
	int to, col;
	T len;
	Edge() {}
	Edge(int to, int col, T len) : to(to), col(col), len(len) {}
	bool operator>(const Edge &r) const { return this->cost > r.cost; }
};

class LCA {
private:

	int N, lg_N;
	vector<int> depth;
	vector<vector<int>> par;

	void build(const vector<vector<Edge<>>> &edges, int root) {

		auto dfs = [&](auto &&f, int now) -> void {
			for (const auto &e : edges[now]) {
				if (par[0][e.to] == -1) {
					par[0][e.to] = now;
					depth[e.to] = depth[now] + 1;
					f(f, e.to);
				}
			}
		};

		par[0][root] = root;
		dfs(dfs, root);

		for (int bit = 0; bit < lg_N; bit++) {
			for (int i = 0; i < N; i++) {
				par[bit + 1][i] = par[bit][par[bit][i]];
			}
		}
	}

	int ancestor(int now, int n) {
		if (n <= 0) return now;
		for (int i = 0, lg_n = 32 - nlz(n); i < lg_n; i++) {
			if (n & (1LL << i)) now = par[i][now];
		}
		return now;
	}

	int nlz(unsigned int x) {
		union {
			unsigned int as_uint32;
			float        as_float;
		} data;
		data.as_float = (float)x + 0.5;
		int n = 158 - (data.as_uint32 >> 23);
		return n;
	}

public:
	LCA(const vector<vector<Edge<>>> &edges, int root = 0) : N(edges.size()), lg_N(32 - nlz(N)), depth(N), par(lg_N + 1, vector<int>(N, -1)) { build(edges, root); }

	int get_lca(int u, int v) {

		if (depth[u] < depth[v]) swap(u, v);
		u = ancestor(u, depth[u] - depth[v]);
		if (u == v) return u;

		for (int i = 32 - nlz(depth[u]); i >= 0; i--) {
			if (par[i][u] != par[i][v]) {
				u = par[i][u];
				v = par[i][v];
			}
		}
		return par[0][u];
	}

	int distance(int u, int v) {
		return depth[u] + depth[v] - 2 * depth[get_lca(u, v)];
	}
};

int main() {

	cin.tie(nullptr);
	ios::sync_with_stdio(false);

	int N, Q;
	cin >> N >> Q;


	vector<vector<Edge<>>> edges(N);
	for (int i = 0; i < N - 1; i++) {
		int u, v, col, len;
		cin >> u >> v >> col >> len;
		u--, v--;
		edges[u].emplace_back(v, col, len);
		edges[v].emplace_back(u, col, len);
	}

	LCA lca(edges);
	// クエリの変更情報は端点+lcaに保存
	vector<map<int, pair<int, lint>>> V(N);
	// クエリ自体は頂点さえ持ってればよい
	vector<Edge<>> q(Q);
	for (int i = 0; i < Q; i++) {
		int x, y, u, v;
		cin >> x >> y >> u >> v;
		u--, v--;
		lint l = lca.get_lca(u, v);
		V[u][i] = { x,y };
		V[v][i] = { x,y };
		V[l][i] = { x,y };
		q[i] = { u,v,l };
	}

	vector<lint> dist(N);
	// dfsでたどった頂点までの色iの辺の合計、辺の長さの合計を保存
	vector<pair<int, lint>> sum(N);
	// V(N)の中身を{diff, *} に書き換え sumを巻き戻しながらdfs
	auto dfs_query = [&](auto &&f, int now, int prev) -> void {
		
		for (auto &e : V[now]) {
			int &x = e.second.first;
			lint &y = e.second.second;
			y = y * sum[x].first - sum[x].second;
		}

		for (const auto &e : edges[now]) {
			int next, col;
			lint len;
			tie(next, col, len) = make_tuple(q[i].to, q[i].col, q[i].len);
			if (next == prev) continue;
			sum[col].first++;
			sum[col].second += len;
			dist[next] = dist[now] + len;
			f(f, next, now);
			sum[col].first--;
			sum[col].second -= len;
		}

	};
	dfs_query(dfs_query, 0, -1);

	for (int i = 0; i < Q; i++) {
		int u, v, l;
		tie(u, v, l) = make_tuple(q[i].to, q[i].col, q[i].len);
		cout << dist[u] + V[u][i].second + dist[v] + V[v][i].second - 2 * (dist[l] + V[l][i].second) << "\n";
	}

	return 0;
}

Compiler output:
a.cc: In lambda function:
a.cc:149:60: error: 'i' was not declared in this scope
  149 |                         tie(next, col, len) = make_tuple(q[i].to, q[i].col, q[i].len);
      |                                                            ^