Graph/tests/aizu_grl_4_a_strongly_connected_cycle_check.test.cpp

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Last update: 2024-06-02 18:23:02+08:00
Problem: https://judge.u-aizu.ac.jp/onlinejudge/description.jsp?id=GRL_4_A

Depends on

Code

#define PROBLEM "https://judge.u-aizu.ac.jp/onlinejudge/description.jsp?id=GRL_4_A"

#include "../../template.h"
#include "../DfsTree/StronglyConnected.h"

void solve() {
    int n, m; cin >> n >> m;
    vector<vector<int>> g(n);
    while (m--) {
        int u, v; cin >> u >> v;
        g[u].push_back(v);
    }
    DirectedDfs tree(g);
    for (auto comp : tree.scc) {
        if (comp.size() > 1) {
            cout << 1 << endl;
            return;
        }
    }
    cout << 0 << endl;
}

#line 1 "Graph/tests/aizu_grl_4_a_strongly_connected_cycle_check.test.cpp"
#define PROBLEM "https://judge.u-aizu.ac.jp/onlinejudge/description.jsp?id=GRL_4_A"

#line 1 "template.h"
#include <bits/stdc++.h>
using namespace std;

#define FOR(i,a,b) for(int i=(a),_b=(b); i<=_b; i++)
#define FORD(i,a,b) for(int i=(a),_b=(b); i>=_b; i--)
#define REP(i,a) for(int i=0,_a=(a); i<_a; i++)
#define EACH(it,a) for(__typeof(a.begin()) it = a.begin(); it != a.end(); ++it)

#define DEBUG(x) { cout << #x << " = "; cout << (x) << endl; }
#define PR(a,n) { cout << #a << " = "; FOR(_,1,n) cout << a[_] << ' '; cout << endl; }
#define PR0(a,n) { cout << #a << " = "; REP(_,n) cout << a[_] << ' '; cout << endl; }

#define sqr(x) ((x) * (x))

// For printing pair, container, etc.
// Copied from https://quangloc99.github.io/2021/07/30/my-CP-debugging-template.html
template<class U, class V> ostream& operator << (ostream& out, const pair<U, V>& p) {
    return out << '(' << p.first << ", " << p.second << ')';
}

template<class Con, class = decltype(begin(declval<Con>()))>
typename enable_if<!is_same<Con, string>::value, ostream&>::type
operator << (ostream& out, const Con& con) {
    out << '{';
    for (auto beg = con.begin(), it = beg; it != con.end(); it++) {
        out << (it == beg ? "" : ", ") << *it;
    }
    return out << '}';
}
template<size_t i, class T> ostream& print_tuple_utils(ostream& out, const T& tup) {
    if constexpr(i == tuple_size<T>::value) return out << ")"; 
    else return print_tuple_utils<i + 1, T>(out << (i ? ", " : "(") << get<i>(tup), tup); 
}
template<class ...U> ostream& operator << (ostream& out, const tuple<U...>& t) {
    return print_tuple_utils<0, tuple<U...>>(out, t);
}

mt19937_64 rng(chrono::steady_clock::now().time_since_epoch().count());
long long get_rand(long long r) {
    return uniform_int_distribution<long long> (0, r-1)(rng);
}

template<typename T>
vector<T> read_vector(int n) {
    vector<T> res(n);
    for (int& x : res) cin >> x;
    return res;
}

void solve();

int main() {
    ios::sync_with_stdio(0); cin.tie(0);
    solve();
    return 0;
}
#line 1 "Graph/DfsTree/StronglyConnected.h"
// Index from 0
// Usage:
// DirectedDfs tree;
// Now you can use tree.scc
//
// Note: reverse(tree.scc) is topo sorted
//
// Tested:
// - (requires scc to be topo sorted) https://judge.yosupo.jp/problem/scc
// - https://cses.fi/problemset/task/1686/
// - (edges have costs) https://oj.vnoi.info/problem/bedao_g16_b
struct DirectedDfs {
    vector<vector<int>> g;
    int n;
    vector<int> num, low, current, S;
    int counter;
    vector<int> comp_ids;
    vector< vector<int> > scc;

    DirectedDfs(const vector<vector<int>>& _g) : g(_g), n(g.size()),
            num(n, -1), low(n, 0), current(n, 0), counter(0), comp_ids(n, -1) {
        for (int i = 0; i < n; i++) {
            if (num[i] == -1) dfs(i);
        }
    }

    void dfs(int u) {
        low[u] = num[u] = counter++;
        S.push_back(u);
        current[u] = 1;
        for (auto v : g[u]) {
            if (num[v] == -1) dfs(v);
            if (current[v]) low[u] = min(low[u], low[v]);
        }
        if (low[u] == num[u]) {
            scc.push_back(vector<int>());
            while (1) {
                int v = S.back(); S.pop_back(); current[v] = 0;
                scc.back().push_back(v);
                comp_ids[v] = ((int) scc.size()) - 1;
                if (u == v) break;
            }
        }
    }

    // build DAG of strongly connected components
    // Returns: adjacency list of DAG
    std::vector<std::vector<int>> build_scc_dag() {
        std::vector<std::vector<int>> dag(scc.size());
        for (int u = 0; u < n; u++) {
            int x = comp_ids[u];
            for (int v : g[u]) {
                int y = comp_ids[v];
                if (x != y) {
                    dag[x].push_back(y);
                }
            }
        }
        return dag;
    }
};
#line 5 "Graph/tests/aizu_grl_4_a_strongly_connected_cycle_check.test.cpp"

void solve() {
    int n, m; cin >> n >> m;
    vector<vector<int>> g(n);
    while (m--) {
        int u, v; cin >> u >> v;
        g[u].push_back(v);
    }
    DirectedDfs tree(g);
    for (auto comp : tree.scc) {
        if (comp.size() > 1) {
            cout << 1 << endl;
            return;
        }
    }
    cout << 0 << endl;
}