Submission #992063

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Source Code Expand

#include <bits/stdc++.h>
using namespace std;
#define int long long
#define REP(i,n) for(int i = 0; i < (int)(n); ++i)
#define DEBUG(x) cerr << #x << " = " << x << endl
struct UnionFind {
  vector<int> data;
  UnionFind(int v) : data(v, -1) {}
  int root(int x) {
    return data[x] < 0 ? x : data[x] = root(data[x]);
  }
  bool same(int x, int y) {
    return root(x) == root(y);
  }
  int size(int x) {
    return -data[root(x)];
  }
  void merge(int x, int y) {
    x = root(x), y = root(y);
    if (x != y) {
      if (size(y) > size(x))
        swap(x, y);
      data[x] += data[y];
      data[y] = x;
    }
  }
};
signed main() {
  ios::sync_with_stdio(false);
  int N, M; cin >> N >> M;
  vector<bool> used_lang(M, false);
  UnionFind U(N + M);
  REP(i, N) {
    int K; cin >> K;
    REP(j, K) {
      int L; cin >> L;
      used_lang[L - 1] = true;
      U.merge(i, N + L - 1);
    }
  }
  int c = N;
  REP(i, M) {
    if(used_lang[i]) ++c;
  }
  if(U.size(0) == c) {
    cout << "YES" << endl;
  }
  else {
    cout << "NO" << endl;
  }
}

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