:heavy_check_mark: library/tree/EdgeVertex.hpp

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Code

#pragma once
#include "library/tree/Tree.hpp"
class EdgeVertex {
    int n, m;
    Tree T;

  public:
    EdgeVertex(int n) : n(n), m(0), T(n * 2 - 1) {}

    int add_edge(int u, int v) {
        assert(0 <= u and u < n);
        assert(0 <= v and v < n);
        int w = n + (m++);
        assert(w < T.n);
        T.add_edge(u, w);
        T.add_edge(w, v);
        return w;
    }

    Tree build(int root = 0) {
        assert(m == n - 1);
        T.build(root);
        return T;
    }
};
#line 2 "library/graph/Graph.hpp"

#include <cassert>
#include <iostream>
#include <vector>

struct Edge {
    int from, to;
    Edge() = default;
    Edge(int from, int to) : from(from), to(to) {}
    operator int() const { return to; }
};

struct Graph {
    int n;
    using edge_type = Edge;
    std::vector<edge_type> edges;

  protected:
    std::vector<int> in_deg;
    bool prepared;
    class OutgoingEdges {
        Graph *g;
        int l, r;

      public:
        OutgoingEdges(Graph *g, int l, int r) : g(g), l(l), r(r) {}
        edge_type *begin() { return &(g->edges[l]); }
        edge_type *end() { return &(g->edges[r]); }
        edge_type &operator[](int i) { return g->edges[l + i]; }
        int size() const { return r - l; }
    };
    class ConstOutgoingEdges {
        const Graph *g;
        int l, r;

      public:
        ConstOutgoingEdges(const Graph *g, int l, int r) : g(g), l(l), r(r) {}
        const edge_type *begin() const { return &(g->edges[l]); }
        const edge_type *end() const { return &(g->edges[r]); }
        const edge_type &operator[](int i) const { return g->edges[l + i]; }
        int size() const { return r - l; }
    };

  public:
    OutgoingEdges operator[](int v) {
        assert(prepared);
        return {this, in_deg[v], in_deg[v + 1]};
    }
    const ConstOutgoingEdges operator[](int v) const {
        assert(prepared);
        return {this, in_deg[v], in_deg[v + 1]};
    }

    bool is_prepared() const { return prepared; }

    Graph() : n(0), in_deg(1, 0), prepared(false) {}
    Graph(int n) : n(n), in_deg(n + 1, 0), prepared(false) {}
    Graph(int n, int m, bool directed = false, int indexed = 1)
        : n(n), in_deg(n + 1, 0), prepared(false) {
        scan(m, directed, indexed);
    }

    void resize(int n) { n = n; }

    void add_arc(int from, int to) {
        assert(!prepared);
        assert(0 <= from and from < n and 0 <= to and to < n);
        edges.emplace_back(from, to);
        in_deg[from + 1]++;
    }
    void add_edge(int u, int v) {
        add_arc(u, v);
        add_arc(v, u);
    }
    void add_arc(const edge_type &e) { add_arc(e.from, e.to); }
    void add_edge(const edge_type &e) { add_edge(e.from, e.to); }

    void scan(int m, bool directed = false, int indexed = 1) {
        edges.reserve(directed ? m : 2 * m);
        while (m--) {
            int u, v;
            std::cin >> u >> v;
            u -= indexed;
            v -= indexed;
            if (directed)
                add_arc(u, v);
            else
                add_edge(u, v);
        }
        build();
    }

    void build() {
        assert(!prepared);
        prepared = true;
        for (int v = 0; v < n; v++)
            in_deg[v + 1] += in_deg[v];
        std::vector<edge_type> new_edges(in_deg.back());
        auto counter = in_deg;
        for (auto &&e : edges)
            new_edges[counter[e.from]++] = e;
        edges = new_edges;
    }

    void graph_debug() const {
#ifndef __LOCAL
        return;
#endif
        assert(prepared);
        for (int from = 0; from < n; from++) {
            std::cerr << from << ";";
            for (int i = in_deg[from]; i < in_deg[from + 1]; i++)
                std::cerr << edges[i].to << " ";
            std::cerr << "\n";
        }
    }
};
#line 3 "library/tree/Tree.hpp"
struct Tree : Graph {
    using Graph::Graph;
    Tree() = default;
    int root = -1;
    std::vector<int> DFS, BFS, depth;

    void scan_root(int indexed = 1) {
        for (int i = 1; i < n; i++) {
            int p;
            std::cin >> p;
            add_edge(p - indexed, i);
        }
        build();
    }
    void scan(int indexed = 1) {
        Graph::scan(n - 1, false, indexed);
        build();
    }

    edge_type &parent(int v) {
        assert(~root and root != v);
        return (*this)[v][0];
    }
    const edge_type &parent(int v) const {
        assert(~root and root != v);
        return (*this)[v][0];
    }

    OutgoingEdges son(int v) {
        assert(~root);
        if (v == root)
            return {this, in_deg[v], in_deg[v + 1]};
        return {this, in_deg[v] + 1, in_deg[v + 1]};
    }

  private:
    void dfs(int v, int pre = -1) {
        for (auto &e : (*this)[v]) {
            if (e.to == pre)
                std::swap((*this)[v][0], e);
            else {
                depth[e.to] = depth[v] + 1;
                dfs(e.to, v);
            }
        }
        DFS.push_back(v);
    }

  public:
    void build(int r = 0) {
        if (!is_prepared())
            Graph::build();
        if (~root) {
            assert(r == root);
            return;
        }
        root = r;
        depth = std::vector<int>(n, 0);
        DFS.reserve(n);
        BFS.reserve(n);
        dfs(root);
        std::queue<int> que;
        que.push(root);
        while (que.size()) {
            int p = que.front();
            que.pop();
            BFS.push_back(p);
            for (const auto &e : son(p))
                que.push(e.to);
        }
    }
};
#line 3 "library/tree/EdgeVertex.hpp"
class EdgeVertex {
    int n, m;
    Tree T;

  public:
    EdgeVertex(int n) : n(n), m(0), T(n * 2 - 1) {}

    int add_edge(int u, int v) {
        assert(0 <= u and u < n);
        assert(0 <= v and v < n);
        int w = n + (m++);
        assert(w < T.n);
        T.add_edge(u, w);
        T.add_edge(w, v);
        return w;
    }

    Tree build(int root = 0) {
        assert(m == n - 1);
        T.build(root);
        return T;
    }
};
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