Submission #10060738

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Source Code Expand

//In The Name Of Allah
#include<bits/stdc++.h>
using namespace std;
#define int long long
#define sz(x) (int)(x.size())
#define double long double 
#define fi first
#define se second
#define pii pair<int, int>

vector<vector<int>> g;

const int N = 1e5 + 100;
vector<vector<int>> lang(N);
vector<bool> visited(N, false);

bool dfs(int v, int par) {
  visited[v] = true;
  bool res = true;
  for (auto &u : g[v]) {
    if (!visited[u]) {
      res &= dfs(u, v);
    }
    else if (visited[u] && u != par) {
      return false;
    }
  }
  return res;
}

signed main() {
  ios::sync_with_stdio(false); cin.tie(nullptr);
  int n, m;
  cin >> n >> m;
  g.resize(n);
  for (int i = 0; i < n; i++) {
    int k;
    cin >> k;
    while (k--) {
      int x;
      cin >> x;
      lang[x].push_back(i);
    }
  }
  for (int i = 1; i <= m; i++) {
    if (2 < sz(lang[i])) {
      cout << "NO\n";
      return 0;
    }
    if (sz(lang[i]) == 2) {
      int u = lang[i][0], v = lang[i][1];
      g[u].push_back(v);
      g[v].push_back(u);
    }
  }
  if (!dfs(0, -1)) {
    cout << "NO\n";
    return 0;
  }
  for (int i = 0; i < n; i++) {
    if (!visited[i]) {
      cout << "NO\n";
      return 0;
    }
  }
  cout << "YES\n";
}

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