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| #include<bits/stdc++.h>
using namespace std;
#define ll long long
const int INF = 0x3f3f3f3f;
const ll inf = 0x3f3f3f3f3f3f3f3f;
const int N = 5e5 + 10;
const ll mod = 1e9 + 7;
int n, q;
vector<int>G[N];
int fa[N], siz[N], dep[N], son[N], topf[N], dfn[N], clk;
void dfs1(int u, int _fa) {
siz[u] = 1; fa[u] = _fa;
for (int v : G[u]) {
if (v == _fa)continue;
dep[v] = dep[u] + 1;
dfs1(v, u);
siz[u] += siz[v];
if (siz[v] > siz[son[u]])son[u] = v;
}
}
void dfs2(int u, int topfa) {
topf[u] = topfa;
dfn[u] = ++clk;
if (!son[u])return;
dfs2(son[u], topfa);
for (int v : G[u]) {
if (!topf[v])dfs2(v, v);
}
}
int LCA(int u, int v) {
while (topf[u] ^ topf[v]) {
dep[topf[u]] < dep[topf[v]] ? v = fa[topf[v]] : u = fa[topf[u]];
}
return dep[u] < dep[v] ? u : v;
}
bool cmp(int x, int y) { return dfn[x] < dfn[y]; }
int top, s[N];
struct E
{
int v, w;
};
vector<E>g[N];
void build(int* h,int k) {
sort(h + 1, h + k + 1, cmp);
s[top = 1] = 1; g[1].clear();
for (int i = 1, l; i <= k; i++) {
if (h[i] != 1) {
l = LCA(h[i], s[top]);
if (l != s[top]) {
while (dfn[l] < dfn[s[top - 1]]) {
g[s[top - 1]].push_back(E{ s[top],dep[s[top]] - dep[s[top - 1]] });
g[s[top]].push_back(E{ s[top - 1],dep[s[top]] - dep[s[top - 1]] });
top--;
}
if (dfn[l] > dfn[s[top - 1]]) {
g[l].clear();
g[l].push_back(E{ s[top],dep[s[top]] - dep[l] });
g[s[top]].push_back(E{ l,dep[s[top]] - dep[l] });
s[top] = l;
}
else {
g[l].push_back(E{ s[top],dep[s[top]] - dep[l] });
g[s[top]].push_back(E{ l,dep[s[top]] - dep[l] });
top--;
}
}
g[h[i]].clear();
s[++top] = h[i];
}
}
for (int i = 1; i < top; i++) {
g[s[i]].push_back(E{ s[i + 1],dep[s[i + 1]] - dep[s[i]] });
g[s[i + 1]].push_back(E{ s[i],dep[s[i + 1]] - dep[s[i]] });
}
}
int ddp[N];
void dfs3(int u, int _fa) {
for (E& e : g[u]) {
if (e.v == _fa)continue;
ddp[e.v] = ddp[u] + e.w;
dfs3(e.v, u);
}
}
int a[N], k;
int main() {
scanf("%d", &n);
for (int i = 1; i < n; i++) {
int u, v;
scanf("%d%d", &u, &v);
G[u].push_back(v);
G[v].push_back(u);
}
dfs1(1, 0);
dfs2(1, 1);
scanf("%d", &q);
while (q--) {
scanf("%d", &k);
for (int i = 1; i <= k; i++) {
scanf("%d", &a[i]);
}
build(a, k);
ddp[1] = 0;
dfs3(1, 0);
int t = 0;
for (int i = 1; i <= k; i++) {
if (ddp[t] <= ddp[a[i]])t = a[i];
}
ddp[t] = 0;
dfs3(t, 0);
int mx = 0;
for (int i = 1; i <= k; i++) {
mx = max(mx, ddp[a[i]]);
}
printf("%d\n", (mx + 1) / 2);
}
return 0;
}
|
