結果

問題 No.2301 Namorientation
コンテスト
ユーザー みここ
提出日時 2023-05-12 22:01:44
言語 C++17
(gcc 13.3.0 + boost 1.87.0)
結果
AC  
実行時間 536 ms / 3,000 ms
コード長 4,163 bytes
コンパイル時間 1,103 ms
コンパイル使用メモリ 84,752 KB
最終ジャッジ日時 2025-02-12 22:48:08
ジャッジサーバーID
（参考情報） 		judge3 / judge2
このコードへのチャレンジ
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ファイルパターン 結果
sample AC * 2
other AC * 30
権限があれば一括ダウンロードができます

ソースコード

diff # 

#include <iostream>
#include <cassert>
#include <queue>
using namespace std;

template <typename T = int>
struct Graph
{
public:
    using value_type = T;

    struct Edge
    {
        int from, to;
        T cost;
        int id;

        operator int() const
        {
            return to;
        }
    };

    Graph() {}

    Graph(int n) : n(n), m(0), g(n) {}

    void add_directed_edge(int from, int to, T cost = 1)
    {
        assert(0 <= from && from < n);
        assert(0 <= to && to < n);
        g[from].push_back((Edge){from, to, cost, m++});
    }

    void add_undirected_edge(int from, int to, T cost = 1)
    {
        assert(0 <= from && from < n);
        assert(0 <= to && to < n);
        g[from].push_back((Edge){from, to, cost, m});
        g[to].push_back((Edge){to, from, cost, m++});
    }

    int size()
    {
        return n;
    }

    int edge_size()
    {
        return m;
    }

    inline const std::vector<Edge> &operator[](const int &u) const
    {
        return g[u];
    }

    inline std::vector<Edge> &operator[](const int &u)
    {
        return g[u];
    }

private:
    int n, m;
    std::vector<std::vector<Edge>> g;
};

template <typename GRAPH>
struct LowLink
{
public:
    using EDGE = typename GRAPH::Edge;
    std::vector<int> articulation;
    std::vector<EDGE> bridge;

    LowLink() {}

    LowLink(GRAPH &g) : n(g.size()), g(g)
    {
        std::vector<int> ord(n, -1);
        std::vector<int> low(n, -1);
        int k = 0;

        auto dfs = [&](auto self, int u, int last_edge_id) -> void
        {
            low[u] = ord[u] = k++;
            int c = 0;
            bool is_artification = false;
            for (auto e : g[u])
            {
                int v = e.to;
                if (e.id == last_edge_id)
                {
                    continue;
                }
                if (ord[v] == -1)
                {
                    c++;
                    self(self, v, e.id);
                    if (last_edge_id != -1 && ord[u] <= low[v])
                    {
                        is_artification = true;
                    }
                    if (ord[u] < low[v])
                    {
                        bridge.push_back(e);
                    }
                    low[u] = std::min(low[u], low[v]);
                }
                low[u] = std::min(low[u], ord[v]);
            }
            is_artification |= (last_edge_id == -1 && c >= 2);
            if (is_artification)
            {
                articulation.push_back(u);
            }
        };

        for (int u = 0; u < n; u++)
        {
            if (ord[u] == -1)
            {
                dfs(dfs, u, -1);
            }
        }
    }

private:
    int n;
    const GRAPH &g;
};

int main()
{
    int n;
    cin >> n;
    Graph<int> g(n);
    int a[200005], b[200005];
    for (int i = 0; i < n; i++)
    {
        cin >> a[i] >> b[i];
        a[i]--;
        b[i]--;
        g.add_undirected_edge(a[i], b[i]);
    }
    int r = -1;
    int eid = -1;
    LowLink<Graph<int>> low(g);
    {
        bool isbridge[200005]{0};
        for (auto e : low.bridge)
        {
            isbridge[e.id] = true;
        }
        for (int i = 0; i < n; i++)
        {
            if (!isbridge[i])
            {
                r = a[i];
                eid = i;
            }
        }
    }
    bool used[200005]{0};
    queue<int> que;
    used[r] = true;
    que.push(r);
    bool ans[200005];
    ans[eid] = true;
    while (que.size())
    {
        int u = que.front();
        que.pop();
        for (auto e : g[u])
        {
            int v = e.to;
            if (used[v] || e.id == eid)
            {
                continue;
            }
            if (a[e.id] == u)
            {
                ans[e.id] = false;
            }
            else
            {
                ans[e.id] = true;
            }
            used[v] = true;
            que.push(v);
        }
    }
    for (int i = 0; i < n; i++)
    {
        if (ans[i])
        {
            cout << "->" << endl;
        }
        else
        {
            cout << "<-" << endl;
        }
    }
}
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