Submission #1696686

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Source Code Expand

#include <bits/stdc++.h>
using namespace std;
/*{{{*/  //template
#define rep(i,n) for(int i=0;i<n;i++)
constexpr int INF = numeric_limits<int>::max()/2;
constexpr long long LINF = numeric_limits<long long>::max()/3;
#define mp make_pair
#define pb push_back
#define eb emplace_back
#define fi first
#define se second
#define all(v) (v).begin(),(v).end()
#define sz(x) (int)(x).size()
#define debug(x) cerr<<#x<<":"<<x<<endl
#define debug2(x,y) cerr<<#x<<","<<#y":"<<x<<","<<y<<endl
//struct fin{ fin(){ cin.tie(0); ios::sync_with_stdio(false); } } fin_;
struct Double{ double d; explicit Double(double x) : d(x){} };
ostream& operator<<(ostream& os,const Double x){ os << fixed << setprecision(20) << x.d; return os; }
template<typename T> ostream& operator<<(ostream& os,const vector<T>& vec){ os << "["; for(const auto& v : vec){ os << v << ","; } os << "]"; return os; }
template<typename T,typename U> ostream& operator<<(ostream& os,const pair<T,U>& p){ os << "(" << p.first << ","<< p.second <<")"; return os; }
template<typename T> ostream& operator<<(ostream& os,const set<T>& st){ os<<"{"; for(T v:st) os<<v<<","; os <<"}"; return os; }
template<typename T,typename U> inline void chmax(T &x,U y){ if(y>x) x = y; }
template<typename T,typename U> inline void chmin(T &x,U y){ if(y<x) x = y; }
typedef long long ll;
typedef unsigned long long ull;
typedef pair<int,int> pii;
typedef vector<int> vi;
typedef vector<vi> vvi;
ll gcd(ll a,ll b){ if(b==0) return a; else return gcd(b,a%b); }
//constexpr double eps = 1e-14; 
constexpr double eps = 1e-10; 
constexpr ll mod = 1e9+7;
const int dx[]={1,0,-1,0} ,dy[] = {0,1,0,-1};
/*}}}*/
class disjoint_set {
    vector<int> p;
public:
    int count;
    disjoint_set(int n) : p(n, -1), count(0) {}
    int root(int i) { return p[i] >= 0 ? p[i] = root(p[i]) : i; }
    bool same(int i, int j) { return root(i) == root(j); }
    int size(int i) { return -p[root(i)]; }
    void merge(int i, int j) {
        count++;
        i = root(i), j = root(j);
        if (i == j) return;
        if (p[i] > p[j]) swap(i, j);
        p[i] += p[j], p[j] = i;
    }
    int size(int i, int j) {
        if(same(i,j)) return size(i);
        else return size(i) + size(j);
    }
};

vector<vi> g;

int main(){
    int N,M;
    cin >> N >> M;
    g.resize(M);
    rep(i,N){
        int k;cin>>k;
        rep(j,k){
            int l;
            cin >> l;
            l--;
            g[l].push_back(i);
        }
    }

    disjoint_set uf(N);

    for(int i=0;i<M;i++){
        for(int j=1;j<g[i].size();j++){
            uf.merge(g[i][0],g[i][j]);
        }
    }

    int sz = uf.size(0);
    if(sz == N){
        cout << "YES" << endl;
    }else{
        cout << "NO" << endl;
    }
}

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