UVA 567 - Risk

#include<bits/stdc++.h>
using  namespace  std;

#define endl     "\n"
#define ll       long long
#define PI       acos(-1.0)
#define test     cout<<"\n****\n"
#define LCM(a,b) ((a/__gcd(a,b))*b)
#define READ(f)  freopen(f, "r", stdin)
#define WRITE(f) freopen(f, "w", stdout)
#define precise  fixed(cout);cout<<setprecision(20)
#define fast     ios_base :: sync_with_stdio(false);cin.tie(NULL);cout.tie(NULL)


#define MAX 30
vector<int>graph[MAX];
int distan[MAX];

int BFS(int from,int to){

    memset(distan,-1,sizeof(distan));
    int root = from;
    distan[root] = 0;

    queue<int>que;
    que.push(root);

    while (!que.empty()){

        int parent = que.front();
        que.pop();

        for(int i=0;i<graph[parent].size();i++){
            int child = graph[parent][i];

            if(distan[child]==-1){
                distan[child] = distan[parent] + 1;
                que.push(child);
            }
        }
    }

    return distan[to];
}

int main(){

    //WRITE("outhudai.txt");
    //fast;
    int n,casee = 1;

    while(cin>>n){

        for(int i=0;i<n;i++){
            int edge;
            cin>>edge;
            graph[1].push_back(edge);
            graph[edge].push_back(1);
        }


        for(int i=2;i<20;i++){
            cin>>n;
            for(int j=0;j<n;j++){
                int edge;
                cin>>edge;
                graph[i].push_back(edge);
                graph[edge].push_back(i);
            }
        }

        int query;
        cin>>query;
        cout<<"Test Set #"<<casee<<endl;
        for(int i=0;i<query;i++){
            int from,to;
            cin>>from>>to;

            printf("%2d to %2d: %d\n",from,to,BFS(from,to));
        }
        cout<<endl;
        for(auto& it: graph){
            it.clear();
        }
        casee++;
    }


    return 0;
}