Cod sursa(job #2693541)

Utilizator anacomoAna-Maria Comorasu anacomo Data 6 ianuarie 2021 12:50:26
Problema Arbore partial de cost minim Scor 100
Compilator cpp-64 Status done
Runda Arhiva educationala Marime 1.93 kb
#include <bits/stdc++.h>
using namespace std;
struct DS
{
    int n;
    vector<int> link, cnt;
    DS(int n) : n(n), cnt(n, 1), link(n, -1) {}
    int root(int a)
    {
        while (link[a] != -1)
            a = link[a];
        return a;
    }

    bool Connected(int a, int b)
    {
        return root(a) == root(b);
    }

    void Link(int a, int b)
    {
        a = root(a);
        b = root(b);
        if (cnt[a] > cnt[b])
            swap(a, b);
        link[a] = b;
        cnt[b] += cnt[a];
    }
};

struct Graph
{
    struct Edge
    {
        int a, b, c;
        Edge(int a, int b, int c) : a(a), b(b), c(c) {}
        bool operator<(const Edge &oth) const
        {
            return c < oth.c;
        }
    };

    int n;
    vector<Edge> edges;
    vector<Edge> mst_edges;

    Graph(int n) : n(n) {}

    void AddEdge(int a, int b, int c)
    {
        edges.emplace_back(a, b, c);
    }

    long long ComputeMST()
    {
        // 1. sortam muchiile.
        sort(edges.begin(), edges.end());

        // 2. pentru fiecare muchie in ordine,
        DS ds(n);
        long long answer = 0;
        for (auto e : edges)
        {
            // daca conecteaza cc diferite, o adaugam la raspuns.
            // se testeaza de m ori
            if (!ds.Connected(e.a, e.b))
            {
                answer += e.c;
                // se apeleaza de maxim n - 1 ori
                ds.Link(e.a, e.b);
                mst_edges.push_back(e);
            }
        }
        return answer;
    }
};

int main()
{
    ifstream cin("apm.in");
    ofstream cout("apm.out");

    int n, m;
    cin >> n >> m;
    Graph G(n);
    for (int i = 0; i < m; ++i)
    {
        int a, b, c;
        cin >> a >> b >> c;
        --a;
        --b;
        G.AddEdge(a, b, c);
    }
    cout << G.ComputeMST() << endl;
    cout << G.mst_edges.size() << endl;
    for (auto e : G.mst_edges)
    {
        cout << e.a + 1 << " " << e.b + 1 << '\n';
    }
    return 0;
}