Submission #11209608

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Source Code Expand

#include <bits/stdc++.h>
using namespace std;
#define rep(i, n) for(int i = 0, i##_len = (n); i < i##_len; ++i)
#define rep2(i, x, n) for(int i = x, i##_len = (n); i < i##_len; ++i)
#define all(n) begin(n), end(n)
using ll = long long;
using P = pair<int, int>;
using vi = vector<int>;
using vl = vector<ll>;
using vs = vector<string>;
using vc = vector<char>;
using vb = vector<bool>;
using vd = vector<double>;
vi dir = {-1, 0, 1, 0, -1, -1, 1, 1, -1};

struct UnionFind {
  vector<int> d;
  UnionFind(int n) : d(n, -1) {}
  int root(int x) {
    if(d[x] < 0) return x;
    return d[x] = root(d[x]);
  }
  bool unite(int x, int y) {
    x = root(x);
    y = root(y);
    if(x == y) return false;
    if(d[x] > d[y]) swap(x, y);
    d[x] += d[y];
    d[y] = x;
    return true;
  }
  bool same(int x, int y) { return root(x) == root(y); }
  int size(int x) { return -d[root(x)]; }
};

int main() {
  int n, m;
  cin >> n >> m;
  UnionFind uf(m);
  vb e(m, false);
  rep(i, n) {
    int k, l0;
    cin >> k >> l0;
    l0--;
    e[l0] = true;
    rep(j, k - 1) {
      int l;
      cin >> l;
      l--;
      e[l] = true;
      uf.unite(l0, l);
    }
  }
  set<int> st;
  rep(i, m) if(e[i]) st.insert(uf.root(i));
  cout << (st.size() == 1 ? "YES" : "NO") << endl;
}

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Judge Result