CTC lexicografic

#include <bits/stdc++.h>
#define nmax 131072

using namespace std;

int N, M, x, y, viz[nmax], nr;
vector < int > G[nmax], GT[nmax], CTC[nmax];
stack < int > S;
vector < pair < int , int > > P;

void Read () {
    cin >> N >> M;
    while (M --) {
        cin >> x >> y;
        G[x].emplace_back (y);
        GT[y].emplace_back (x);
    }
}

void DFSP (int nod) {
    viz[nod] = 1;
    for (size_t i = 0; i < G[nod].size(); ++i)
    if (!viz[G[nod][i]]) DFSP (G[nod][i]);
    S.push (nod);
}

void DFSM (int nod) {
    viz[nod] = 2;
    CTC[nr].emplace_back (nod);
    for (size_t i = 0; i < GT[nod].size(); ++i)
    if (viz[GT[nod][i]] == 1) DFSM (GT[nod][i]);
}

bool fcmp (pair < int , int > a, pair < int , int > b) {
    return a.second < b.second;
}

void Solve () {
    for (int i = 1; i <= N; ++i) if (!viz[i]) DFSP (i);
    while (!S.empty()) {
        int nod = S.top ();
        S.pop ();
        if (viz[nod] == 1) {
            nr ++;
            DFSM (nod);
        }
    }
    for (int i = 1; i <= nr; ++i) {
        sort (CTC[i].begin(), CTC[i].end());
        P.push_back ({i, CTC[i][0]});
    }
    sort (P.begin(), P.end(), fcmp);
    for (int i = 0; i < nr; ++i, cout << '\n')
    for (size_t j = 0; j < CTC[P[i].first].size(); ++j)
    cout << CTC[P[i].first][j] << " ";
}

void Boost () {
    ios::sync_with_stdio(false);
    cin.tie (0);
    cout.tie (0);
}

int main()
{
    Boost ();
    Read ();
    Solve ();
    return 0;
}