tests/graph/bridges.test.cpp

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• Last update: 2021-09-12 23:20:08-04:00
• Problem: https://judge.u-aizu.ac.jp/onlinejudge/description.jsp?id=GRL_3_B

Depends on

• graph/edge_types.hpp
• graph/tarjan_undirected.hpp
• template.hpp
• tests/test_utils.hpp

Code

#define PROBLEM "https://judge.u-aizu.ac.jp/onlinejudge/description.jsp?id=GRL_3_B"
#include "../../template.hpp"
#include "../test_utils.hpp"
#include "../../graph/tarjan_undirected.hpp"
#include "../../graph/edge_types.hpp"

const int MN = 1e5 + 1;
int N, M,
    A[MN], B[MN];
vector<pii> g[MN];

int main() {
    fast_io();
    cin >> N >> M;
    for (int i = 0; i < M; i++) {
        int a, b; cin >> a >> b; a++; b++;
        g[a].eb(b, i);
        g[b].eb(a, i);
        A[i] = a; B[i] = b;
    }

    Tarjan<vector<pii>[MN], IndexedEdge, BRIDGES> brid; brid.solve(N, g);
    vector<pii> res;
    for (auto x : brid.bridges)
        res.eb(min(A[x], B[x])-1, max(A[x], B[x])-1);
    sort(all(res));
    for (auto [a, b] : res)
        print(a, b);
}

#line 1 "tests/graph/bridges.test.cpp"
#define PROBLEM "https://judge.u-aizu.ac.jp/onlinejudge/description.jsp?id=GRL_3_B"
#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 "tests/test_utils.hpp"

// I/O
template <typename T> void print(T v) {
    cout << v << '\n';
}

template <typename T, typename... Rest> void print(T v, Rest... vs) {
    cout << v << ' ';
    print(vs...);
}

void fast_io() {
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
}

// Reading operators
template <typename T, typename U> istream& operator>>(istream& in, pair<T, U> &o) {
    return in >> o.first >> o.second;
}

// Read helpers
int readi() {
    int x; cin >> x;
    return x;
}

ll readl() {
    ll x; cin >> x;
    return x;
}

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

// Functional stuff
template <typename T> vector<pair<int, T>> enumerate(vector<T> v, int start = 0) {
    vector<pair<int, T>> res;
    for (auto &x : v)
        res.emplace_back(start++, x);
    return res;
}

#line 3 "graph/tarjan_undirected.hpp"

const int BICONNECTED_COMPONENTS = 1 << 0, ARTICULATION_POINTS = 1 << 1, BRIDGES = 1 << 2;
template <typename GraphType, typename EdgeType, int MODE> struct Tarjan {
    EdgeType E;
    int cord = 0;
    vector<int> ord, low;
    vector<pii> stk;

    vector<int> articulation_points;
    vector<int> bridges;
    vector<vector<pii>> components;

    void solve(int N, GraphType &g) {
        cord = 0;
        ord.assign(N+1, 0); low.assign(N+1, 0);
        stk.clear();
        if (MODE & BICONNECTED_COMPONENTS) components.clear();
        if (MODE & ARTICULATION_POINTS) articulation_points.clear();
        if (MODE & BRIDGES) bridges.clear();

        function<void(int, int)> tarjan = [&] (int c, int pi) {
            bool artic = false;
            int cc = 0;

            ord[c] = low[c] = ++cord;
            for (auto _to : g[c]) {
                int to = E.v(_to), toi = E.i(_to);
                if (toi != pi) {
                    if (!ord[to]) {
                        if (MODE & BICONNECTED_COMPONENTS) stk.emplace_back(c, to);
                        if (MODE & ARTICULATION_POINTS) cc++;
                        tarjan(to, toi);
                        low[c] = min(low[c], low[to]);

                        // we got an articulation point bois :sunglasses:
                        if (low[to] >= ord[c]) {
                            if (MODE & ARTICULATION_POINTS) artic = true;
                            if (MODE & BICONNECTED_COMPONENTS) {
                                components.push_back(vector<pii>());
                                int u, v;
                                do {
                                    auto _e = stk.back();
                                    stk.pop_back();
                                    tie(u, v) = _e;
                                    components.back().emplace_back(u, v);
                                } while (u != c || v != to);
                            }
                        }
                        if (MODE & BRIDGES) {
                            if (low[to] > ord[c])
                                bridges.push_back(toi);
                        }
                    } else if (ord[to] < ord[c]) {
                        if (MODE & BICONNECTED_COMPONENTS) stk.emplace_back(c, to);
                        low[c] = min(low[c], ord[to]);
                    }
                }
            }

            if (MODE & ARTICULATION_POINTS)
                if ((pi != -1 && artic) || (pi == -1 && cc > 1))
                    articulation_points.push_back(c);
        };
        for (int i = 1; i <= N; i++)
            if (!ord[i])
                tarjan(i, -1);
    }

#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 3 "graph/edge_types.hpp"

struct Edge {
    using EdgeType = int;
    int v(EdgeType e) { return e; }
    int w(EdgeType e) { return 1; }
    int i(EdgeType e) { throw domain_error("no information on edge indices"); }
    EdgeType swapNode(EdgeType e, int v) { return v; }
};
template <typename T> struct WeightedEdge {
    using EdgeType = pair<int, T>; using WeightType = T;
    int v(EdgeType e) { return e.first; }
    T w(EdgeType e) { return e.second; }
    int i(EdgeType e) { throw domain_error("no information on edge indices"); }
    EdgeType swapNode(EdgeType e, int v) { return {v, w(e)}; }
};
struct IndexedEdge {
    using EdgeType = pair<int, int>;
    int v(EdgeType e) { return e.first; }
    int w(EdgeType e) { return 1; }
    int i(EdgeType e) { return e.second; }
    EdgeType swapNode(EdgeType e, int v) { return {v, i(e)}; }
};
template <typename T> struct WeightedIndexedEdge {
    using EdgeType = tuple<int, T, int>; using WeightType = T;
    int v(EdgeType e) { return get<0>(e); }
    T w(EdgeType e) { return get<1>(e); }
    int i(EdgeType e) { return get<2>(e); }
    EdgeType swapNode(EdgeType e, int v) { return {v, w(e), i(e)}; }
};
#line 6 "tests/graph/bridges.test.cpp"

const int MN = 1e5 + 1;
int N, M,
    A[MN], B[MN];
vector<pii> g[MN];

int main() {
    fast_io();
    cin >> N >> M;
    for (int i = 0; i < M; i++) {
        int a, b; cin >> a >> b; a++; b++;
        g[a].eb(b, i);
        g[b].eb(a, i);
        A[i] = a; B[i] = b;
    }

    Tarjan<vector<pii>[MN], IndexedEdge, BRIDGES> brid; brid.solve(N, g);
    vector<pii> res;
    for (auto x : brid.bridges)
        res.eb(min(A[x], B[x])-1, max(A[x], B[x])-1);
    sort(all(res));
    for (auto [a, b] : res)
        print(a, b);
}

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