calling circles uva (using tarjan scc)

// Those who cannot remember the past are
// condemned to repeat it (use DP -_-)
// - George Santayana

#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>

using namespace std;
using namespace __gnu_pbds;

#define all(v) v.begin(), v.end()
#define rall(v) v.rbegin(), v.rend()
#define ll long long
#define ull unsigned long long
#define MOD 1000000007
#define PI acos(-1)
//#define ceil(a, b) (((a) / (b)) + ((a) % (b) ? 1 : 0))
#define imin INT_MIN
#define imax INT_MAX
#define llmax LLONG_MAX
#define llmin LLONG_MIN
#define inf 2000000000
#define nl '\n'
#define ppcnt __builtin_popcount
#define ppcntll __builtin_popcountll
#define clz __builtin_clz
#define clzll __builtin_clzll
#define ctz __builtin_ctz
#define ctzll __builtin_ctzll
#define modulo(a, b, mod) ((((a) % (mod)) + ((b) % (mod))) % (mod))
#define cnte(v, x) count(all(v), (x))
#define mine(v) min_element(all(v))
#define maxe(v) max_element(all(v))
#define updmin(a, b) a = min(a, b)
#define updmax(a, b) a = max(a, b)
#define findmod(x, m) x = ((x) % (m) + (m)) % m
#define getmod(x, m) ((x) % (m) + (m)) % (m)
#define debug(x) cout << "x: " << (x) << nl;
#define debug2(x, y) cout << "x: " << (x) << " y: " << y << nl;
#define ordered_set tree<pair<int, int>, null_type, less<>, rb_tree_tag, tree_order_statistics_node_update>
#define ordered_map tree<int, int, less<>, rb_tree_tag, tree_order_statistics_node_update>

//vector<int> dx = {0, 0, 1, -1, 1, 1, -1, -1}, dy = {1, -1, 0, 0, 1, -1, 1, -1};
vector<int> dx = {0, 0, 1, -1}, dy = {1, -1, 0, 0};

template<typename T = int>
istream &operator>>(istream &in, vector<pair<int, int>> &v) {
    for (auto &[x, y]: v) in >> x >> y;
    return in;
}

template<typename T = int>
istream &operator>>(istream &in, vector<T> &v) {
    for (T &i: v) in >> i;
    return in;
}

template<typename T = int>
ostream &operator<<(ostream &out, const vector<T> &v) {
    for (const T &x: v)
        out << x << ' ';
    return out;
}

template<typename T = pair<int, int>>
ostream &operator<<(ostream &out, const vector<pair<int, int>> &v) {
    for (auto &[x, y]: v) {
        out << x << ' ' << y << nl;
    }
    return out;
}

void Start_Crushing() {
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
    cout.tie(nullptr);
#ifndef ONLINE_JUDGE
    freopen("input.txt", "r", stdin);
    freopen("output.txt", "w", stdout);
#endif
}

map<string, vector<string>> adj;
map<string, int> dfs_num, dfs_low;
int counter;
stack<string> order;
map<string, bool> vis;
vector<vector<string>> sccs;

void tarjan_scc(string& src){
    dfs_num[src] = dfs_low[src] = counter++;
    order.push(src);
    vis[src] = true;

    for(auto& nxt : adj[src]){
        if(not dfs_num[nxt]){
            tarjan_scc(nxt);
        }
        if(vis[nxt])
            dfs_low[src] = min(dfs_low[src], dfs_low[nxt]);
    }
    if(dfs_low[src] == dfs_num[src]){

        vector<string> scc;

        while(not order.empty()){
            scc.push_back(order.top());
            order.pop();
            vis[scc.back()] = false;
            if(scc.back() == src)
                break;
        }

        sccs.emplace_back(scc);
    }
}

void solve(int tc) {
    // we wanna find all the SCCs and count only the SCC which is greater than 2

    int n, m; cin >> n >> m;
    while(n and m){
        adj.clear();
        dfs_num.clear(), dfs_low.clear(), vis.clear(), sccs.clear();
        counter = 1;

        vector<string> people;

        for(int i = 0; i < m; i++){
            string u, v; cin >> u >> v;
            adj[u].emplace_back(v);
            if(not vis[u]) {
                people.emplace_back(u);
                vis[u] = true;
            }
            if(not vis[v]) {
                people.emplace_back(v);
                vis[v] = true;
            }
        }
        vis.clear();

        for(auto& person : people){
            if(not dfs_num[person])
                tarjan_scc(person);
        }

        cout << "Calling circles for data set " << tc++ << ":\n";
        for(auto& scc : sccs){
            for(int i = 0; i < scc.size(); i++){
                if(i)
                    cout << ", ";
                cout << scc[i];
            }
            cout << nl;
        }
        cout << nl;
        cin >> n >> m;
    }
}

void set_file(string &file_name) {
    freopen((file_name + ".in").c_str(), "r", stdin);
    freopen((file_name + ".out").c_str(), "w", stdout);
}

int main() {
    Start_Crushing();

//    string file_name = "";
//    set_file(file_name);

    int t = 1;
//    /*Multiple test cases?*/ cin >> t;
    while (t--) {
        solve(1);
//        if (!t)
//            break;
//        cout << nl;
    }

//    for(int tc = 1; tc <= t; tc++){
////        cout << "Calling circles for data set " << tc << ":\n";
//        solve(tc);
////        if(tc != t)
////            cout << nl;
//        printf("\n");
//    }

    return 0;
}