Submission #991908

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Source Code Expand

#include <bits/stdc++.h>

using namespace std;

typedef long double ld;
typedef long long ll;

const int M = 200100;

int n, m;

int p[M];

void ini() {
  iota(p, p + M, 0);
}

int get(int x) {
  return p[x] = p[x] == x ? x : get(p[x]);
}

void uni(int x, int y) {
  x = get(x);
  y = get(y);
  p[x] = y;
}

void read() {
  cin >> n >> m;
  for (int i = 0; i < n; ++i) {
    int k;
    cin >> k;
    for (int j = 0; j < k; ++j) {
      int x;
      cin >> x;
      uni(i, n + x);
    }
  }

  for (int i = 0; i < n; ++i)
    if (get(i) != get(0)) {
      cout << "NO\n";
      exit(0);
    }
  cout << "YES\n";
}

int main() {
#ifdef LOCAL
  assert(freopen("c.in", "r", stdin));
#endif

  ios_base::sync_with_stdio(false);

  ini();
  read();

}

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