1063 Set Similarity

#include<iostream>
#include<set>
using namespace std;

set<int>S[51];
set<int>::iterator it1,it2;

int main()
{
    int N,i,j,k;
    cin>>N;
    for(i=1;i<=N;i++){
        scanf("%d",&j);
        while(j--){
            scanf("%d",&k);
            S[i].insert(k);
        }
    }
    
    int K;
    cin>>K;
    while(K--){
        scanf("%d %d",&i,&j);
        
        int Nc=0;
        for(it1=S[i].begin(),it2=S[j].begin();it1!=S[i].end()&&it2!=S[j].end();){
            if(*it1<*it2){
                ++it1;
            }
            else if(*it1>*it2){
                ++it2;
            }
            else{
                ++Nc;
                ++it1;
                ++it2;
            }
        }
        int Nt=S[i].size()+S[j].size()-Nc;
        printf("%.1f%c\n",100.0*Nc/Nt,'%');
        
    }
}
//Nc common
//Nt total