graph/scc.hpp

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• Last update: 2021-09-12 23:20:08-04:00
• Include: #include "graph/scc.hpp"

Depends on

• template.hpp

Verified with

• tests/graph/scc.test.cpp

Code

#pragma once
#include "../template.hpp"

template <typename GraphType, typename EdgeType> struct SCC {
    EdgeType E;
    int cord = 0;
    vector<int> ord, low, stk;
    vector<bool> instk;

    vector<vector<int>> solve(int N, GraphType &g) {
        ord.assign(N+1, 0);
        low.assign(N+1, 0);
        instk.assign(N+1, false);
        stk.clear();
        cord = 0;

        vector<vector<int>> cs;
        function<void(int)> tarjan = [&] (int c) {
            ord[c] = low[c] = ++cord;
            instk[c] = true;
            stk.push_back(c);

            for (auto _to : g[c]) {
                int to = E.v(_to);
                if (!ord[to]) {
                    tarjan(to);
                    low[c] = min(low[c], low[to]);
                } else if (instk[to])
                    low[c] = min(low[c], ord[to]);
            }

            if (low[c] == ord[c]) {
                int u;
                cs.push_back(vector<int>());
                do {
                    u = stk.back();
                    instk[u] = false;
                    stk.pop_back();
                    cs.back().push_back(u);
                } while (u != c);
            }
        };
        for (int i = 1; i <= N; i++)
            if (!ord[i])
                tarjan(i);

        return cs;
    }

#if __cplusplus == 201703L // CPP17 only things
    void bind(opt_ref<vector<int>> ord0, opt_ref<vector<int>> low0) {
        if (ord0) ord.swap(*ord0);
        if (low0) low.swap(*low0);
    }
#endif
};

#line 2 "template.hpp"
#include <bits/stdc++.h>
#define DEBUG 1
using namespace std;

// Defines
#define fs first
#define sn second
#define pb push_back
#define eb emplace_back
#define mpr make_pair
#define mtp make_tuple
#define all(x) (x).begin(), (x).end()
// Basic type definitions
#if __cplusplus == 201703L // CPP17 only things
template <typename T> using opt_ref = optional<reference_wrapper<T>>; // for some templates
#endif
using ll = long long; using ull = unsigned long long; using ld = long double;
using pii = pair<int, int>; using pll = pair<long long, long long>;
#ifdef __GNUG__
// PBDS order statistic tree
#include <ext/pb_ds/assoc_container.hpp> // Common file
#include <ext/pb_ds/tree_policy.hpp>
using namespace __gnu_pbds;
template <typename T, class comp = less<T>> using os_tree = tree<T, null_type, comp, rb_tree_tag, tree_order_statistics_node_update>;
template <typename K, typename V, class comp = less<K>> using treemap = tree<K, V, comp, rb_tree_tag, tree_order_statistics_node_update>;
// HashSet
#include <ext/pb_ds/assoc_container.hpp>
template <typename T, class Hash> using hashset = gp_hash_table<T, null_type, Hash>;
template <typename K, typename V, class Hash> using hashmap = gp_hash_table<K, V, Hash>;
const ll RANDOM = chrono::high_resolution_clock::now().time_since_epoch().count();
struct chash { ll operator()(ll x) const { return x ^ RANDOM; } };
#endif
// More utilities
int SZ(string &v) { return v.length(); }
template <typename C> int SZ(C &v) { return v.size(); }
template <typename C> void UNIQUE(vector<C> &v) { sort(v.begin(), v.end()); v.resize(unique(v.begin(), v.end()) - v.begin()); }
template <typename T, typename U> void maxa(T &a, U b) { a = max(a, b); }
template <typename T, typename U> void mina(T &a, U b) { a = min(a, b); }
const ll INF = 0x3f3f3f3f, LLINF = 0x3f3f3f3f3f3f3f3f;
#line 3 "graph/scc.hpp"

template <typename GraphType, typename EdgeType> struct SCC {
    EdgeType E;
    int cord = 0;
    vector<int> ord, low, stk;
    vector<bool> instk;

    vector<vector<int>> solve(int N, GraphType &g) {
        ord.assign(N+1, 0);
        low.assign(N+1, 0);
        instk.assign(N+1, false);
        stk.clear();
        cord = 0;

        vector<vector<int>> cs;
        function<void(int)> tarjan = [&] (int c) {
            ord[c] = low[c] = ++cord;
            instk[c] = true;
            stk.push_back(c);

            for (auto _to : g[c]) {
                int to = E.v(_to);
                if (!ord[to]) {
                    tarjan(to);
                    low[c] = min(low[c], low[to]);
                } else if (instk[to])
                    low[c] = min(low[c], ord[to]);
            }

            if (low[c] == ord[c]) {
                int u;
                cs.push_back(vector<int>());
                do {
                    u = stk.back();
                    instk[u] = false;
                    stk.pop_back();
                    cs.back().push_back(u);
                } while (u != c);
            }
        };
        for (int i = 1; i <= N; i++)
            if (!ord[i])
                tarjan(i);

        return cs;
    }

#if __cplusplus == 201703L // CPP17 only things
    void bind(opt_ref<vector<int>> ord0, opt_ref<vector<int>> low0) {
        if (ord0) ord.swap(*ord0);
        if (low0) low.swap(*low0);
    }
#endif
};

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