90pts 求调

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

const int maxn = 1e5 + 50;
typedef long long ll;

int head[maxn], cnt;
struct edge {
	int to, nxt;
} e[maxn << 1]; 

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

int n, q;
int f[maxn][22], dep[maxn];
int a, b, c, d;

void dfs(int u, int fa) {
	dep[u] = dep[fa] + 1, f[u][0] = fa;
	for (int i = head[u]; i; i = e[i].nxt) {
		int v = e[i].to;
		if (v == fa) continue;
		dfs(v, u);
	}
}

int lca(int u, int v) {
	if (dep[u] < dep[v]) swap(u, v);
	for (int i = 20; i >= 0; i--) if (dep[f[u][i]] >= dep[v]) u = f[u][i];
	if (u == v) return u;
	for (int i = 20; i >= 0; i--) if (f[u][i] != f[v][i]) u = f[u][i], v = f[v][i];
	return f[u][0];
}

int l(int x, int y) {
	return dep[x] + dep[y] - 2 * dep[lca(x, y)];
}

int main() {
    cin >> n >> q;
    for (int i = 1, u, v; i < n; i++) {
    	cin >> u >> v;
    	add(u, v), add(v, u);
	}
	dfs(1, 0);
	for (int j = 1; (1 << j) <= n; j++) 
		for (int i = 1; i <= n; i++) f[i][j] = f[f[i][j - 1]][j - 1];
	for (int i = 1; i <= q; i++) {
		int a, b, c, d;
		cin >> a >> b >> c >> d;
		int lca1 = lca(a, b), lca2 = lca(c, d);
		if (dep[lca1] > dep[lca2]) {
			if (l(c, lca1) + l(lca1, d) == l(c, d)) cout << "Y" << '\n';
			else cout << "N" << '\n';
		}
		else if (dep[lca1] < dep[lca2]) {
			if (l(a, lca2) + l(lca2, b) == l(a, b)) cout << "Y" << '\n';
			else cout << "N" << '\n';
		}
		// cout << lca1 << ' ' << lca2 << '\n';
		else cout << "Y" << '\n';
	}
    return 0;
}