Submission #1495996

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Source Code Expand

#include<bits/stdc++.h>
using namespace std;
int tree[100010];
int root(int x){return tree[x] == x ? x : tree[x] = root(tree[x]);}
void unite(int a , int b){tree[root(a)] = root(b);}

int main(){
	int n , m;	cin >> n >> m;
	for(int i = 0; i < n; i++)	tree[i] = i;
	int k;
	vector <vector <int> > l(m);
	for(int i = 0; i < n; i++){
		cin >> k;
		int va;
		for(int j = 0; j < k; j++){
			cin >> va;
			va--;
			l[va].push_back(i);
		}
	}
	for(int i = 0; i < m; i++){
		while(l[i].size() >= 2){
			cout << l[i][0] << " " << l[i][l[i].size() - 1] << endl;
			unite(l[i][0] , l[i][l[i].size() - 1]);
			l[i].pop_back();
		}
	}
	for(int i = 0; i < n - 1; i++)
		if(root(i) != root(i + 1)){
			cout << "NO" << endl;
			return 0;
		}
	cout << "YES" << endl;
	return 0;
}

Submission Info

Judge Result