graph/get_edges.hpp

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• Last update: 2024-01-25 10:46:02+09:00
• Include: #include "graph/get_edges.hpp"

Depends on

• graph/graph_template.hpp

Required by

• Kruskal's algorithm (クラスカル法) (graph/kruskal.hpp)

Verified with

• verify/aoj_grl/aoj_grl_2_a.test.cpp

Code

#pragma once

#include "graph/graph_template.hpp"

template <class T> Edges<T> get_edges(Graph<T> &G) {
    int N = (int)G.size(), M = 0;
    for (int i = 0; i < N; i++) {
        for (auto &&e : G[i]) {
            M = std::max(M, e.id + 1);
        }
    }
    Edges<T> es(M);
    for (int i = N - 1; i >= 0; i--) {
        for (auto &&e : G[i]) {
            es[e.id] = e;
        }
    }
    return es;
}

#line 2 "graph/get_edges.hpp"

#line 2 "graph/graph_template.hpp"

#include <vector>
template <class T> struct Edge {
    int from, to;
    T cost;
    int id;

    Edge() = default;
    Edge(int from, int to, T cost = 1, int id = -1) : from(from), to(to), cost(cost), id(id) {}

    friend std::ostream &operator<<(std::ostream &os, const Edge<T> &e) {
        // output format: "{ id : from -> to, cost }"
        return os << "{ " << e.id << " : " << e.from << " -> " << e.to << ", " << e.cost << " }";
    }
};

template <class T> using Edges = std::vector<Edge<T>>;
template <class T> using Graph = std::vector<std::vector<Edge<T>>>;
#line 4 "graph/get_edges.hpp"

template <class T> Edges<T> get_edges(Graph<T> &G) {
    int N = (int)G.size(), M = 0;
    for (int i = 0; i < N; i++) {
        for (auto &&e : G[i]) {
            M = std::max(M, e.id + 1);
        }
    }
    Edges<T> es(M);
    for (int i = N - 1; i >= 0; i--) {
        for (auto &&e : G[i]) {
            es[e.id] = e;
        }
    }
    return es;
}

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