ARC148C AC

// Problem: C - Lights Out on Tree
// Contest: AtCoder - AtCoder Regular Contest 148
// URL: https://atcoder.jp/contests/arc148/tasks/arc148_c
// Memory Limit: 1024 MB
// Time Limit: 3000 ms
//
// Powered by CP Editor (https://cpeditor.org)

#include <assert.h>
#include <bits/stdc++.h>
using namespace std;
#define dbg(...) logger(#__VA_ARGS__, __VA_ARGS__)
template <typename... Args> void logger(string vars, Args &&... values)
{
    cerr << vars << " = ";
    string delim = "";
    (..., (cerr << delim << values, delim = ", "));
    cerr << endl;
}

template <class T> inline auto vv(int m) { return vector<vector<T>>(m, vector<T>(m)); }
template <class T> inline auto vv(int m, int n) { return vector<vector<T>>(m, vector<T>(n)); }
template <class T, T init> inline auto vv(int m) { return vector<vector<T>>(m, vector<T>(m, init)); }
template <class T, T init> inline auto vv(int m, int n) { return vector<vector<T>>(m, vector<T>(n, init)); }

template <class T> using mpq = priority_queue<T, vector<T>, greater<T>>;

using ll = long long;
using pii = pair<int, int>;
using vl = vector<ll>;
using vi = vector<int>;

int n, q;
vi fa, cnt;
vi g[200003];

int main(int argc, char **argv)
{
    cin >> n >> q;
    cnt = fa = vi(n + 1);
    for (int i = 2; i <= n; ++i)
        cin >> fa[i], g[fa[i]].push_back(i), cnt[fa[i]]++;
    for (int i = 0; i < q; ++i) {
        int m, v;
        cin >> m;
        set<int> vs;
        for (int j = 0; j < m; ++j)
            cin >> v, vs.insert(v);
        int ans = 0;
        for (int u : vs) {
            ans += cnt[u];
            if (vs.count(fa[u]))
                --ans;
            else
                ++ans;
        }
        cout << ans << endl;
    }
    return 0;
};