Alive Fossils

1.
#include <bits/stdc++.h>
using namespace std;
#define ll long long
const ll N=1e10+5;
int main()
{
	ll n,c,f=0;
	cin>>n;
	vector<string>s;
	vector<string>b;
	ll i,j=0;
	for(i=0;i<n;i++)
	{
		cin>>c;
		while(c--)
		{
			string a;
			cin>>a;
			s.push_back(a);
			j++;
		}
	}
	sort(s.begin(), s.end());
	ll k=0;
	for(i=0;i<j-1;i++)
	{
		if(s[i]==s[i+1])
          k++;
		else 
          k=0;
		if(k==n-1)
            b.push_back(s[i]);
	}
    if(n!=1)
    {
	cout<<b.size()<<endl;
	for(i=0;i<b.size();i++)cout<<b[i]<<endl;
    }
    else 
    {
        cout<<s.size()<<endl;
        for(i=0;i<s.size();i++)cout<<s[i]<<endl;
    }
	return 0;
}

2.
#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
map<string,ll>mp;
signed main()
{
	ll t;
	cin>>t;
    ll p=t;
	while(t--)
	{
		ll n;
		string x;
		cin>>n;
		while(n--)
		{
			cin>>x;
			mp[x]++;
		}
	}
	ll ans=0;
	for(auto it : mp)
		if(it.second>=p)
			ans++;
			
	cout<<ans<<endl;
	for(auto it : mp)
		if(it.second>=p)
			cout<<it.first<<endl;

	mp.clear();
	return 0;
}

map? 详见:https://blog.csdn.net/qq_50285142/article/details/120368977