Метро

#include <bits/stdc++.h>

using namespace std;

const unsigned long long MOD=(long long)1e9+7;
const long long INF=(2*(long long)1e9);
long long cycle_start,cycle_end;

vector<pair<int,int> > cycle;

long long p[(long long)1e5+1]={};

int ans=0;
int n,m;

bool used[101][101]={};
pair<int,int> parent[101][101];
int d[101][101];

int main()
{
    ios::sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);
    //freopen("knight1.in","r",stdin);
    //freopen("knight1.out","w",stdout);
    cin>>n;
    cin>>m;
    int qq;
    int a[2];
    vector<vector<pair<int,int> > > g(n+1); /// 1 - v 2 - line
    while(m--)
    {
        cin>>qq;
        for(int i=0;i<qq;i++)
        {
            cin>>a[i%2];
            if(i>0)
            {
                g[a[1]].push_back(make_pair(a[0],m+1));
                g[a[0]].push_back(make_pair(a[1],m+1));
            }
        }
    }
    int s,f;
    cin>>s>>f;
    int d[n+1];
    for(int i=0;i<=n;i++)
    {
        d[i]=(int)1e9;
    }
    d[s]=0;
    set<pair<int,pair<int,int> > > q;
    q.insert(make_pair(0,make_pair(s,-1))); /// 1 - len 2 - v 3 - line;
    int v,len,line;
    while(!q.empty())
    {
        v=q.begin()->second.first;
        line=q.begin()->second.second;
        len=q.begin()->first;
        q.erase(q.begin());
        for(auto x : g[v])
        {
            if(len+(bool)(x.second!=line && line!=-1)<d[x.first])
            {
                d[x.first]=len+(bool)(x.second!=line && line!=-1);
                q.insert(make_pair(len+(bool)(x.second!=line && line!=-1),make_pair(x.first,x.second)));
            }
        }
    }
    cout<<(d[f]==(int)1e9 ? -1 : d[f]);
}