Cod sursa(job #2629650)

Utilizator EckchartZgarcea Robert-Andrei Eckchart Data 22 iunie 2020 08:15:19
Problema Arbore partial de cost minim Scor 100
Compilator cpp-64 Status done
Runda Arhiva educationala Marime 1.99 kb
#include <fstream>
#include <vector>
#include <algorithm>
using namespace std;
using pii = pair<int, int>;
int N, M;
vector<int> parent, tree_size;
vector<pair<int, pii>> adj;


void make_set(const int &vertex)
{
    parent[vertex] = vertex;
    tree_size[vertex] = 1;
}


int find_leader(const int &vertex)
{
    if (parent[vertex] == vertex)
    {
        return vertex;
    }

    return parent[vertex] = find_leader(parent[vertex]);
}


void unite_sets(int &set1, int &set2)
{
    set1 = find_leader(set1);
    set2 = find_leader(set2);

    if (set1 != set2)
    {
        if (tree_size[set1] < tree_size[set2])
        {
            swap(set1, set2);
        }

        tree_size[set1] += tree_size[set2];
        parent[set2] = set1;
    }
}


void Kruskal()
{
    vector<pii> MST_edges;
    int total_weight = 0;

    for (int node = 1; node <= N; ++node)
    {
        make_set(node);
    }

    sort(begin(adj), end(adj), greater<pair<int, pii>>());

    for (int i = 1; i < N; ++i)
    {
        int CC1, CC2, leader1, leader2;

        do
        {
            CC1 = adj.back().second.first;
            CC2 = adj.back().second.second;
            leader1 = find_leader(CC1);
            leader2 = find_leader(CC2);
            adj.pop_back();
        } while (leader1 == leader2);

        total_weight += adj.back().first;
        MST_edges.push_back({CC1, CC2});
        unite_sets(leader1, leader2);
    }

    ofstream fout("apm.out");

    fout << total_weight << "\n" << N - 1 << "\n";
    for (const pii &MST_edge : MST_edges)
    {
        fout << MST_edge.first << " " << MST_edge.second << "\n";
    }
}


int main()
{
    ifstream fin("apm.in");

    fin >> N >> M;
    parent.resize(N + 1);
    tree_size.resize(N + 1);
    
    while (M--)
    {
        int i, j, weight;
        fin >> i >> j >> weight;

        adj.push_back({weight, {i, j}});
        adj.push_back({weight, {j, i}});
    }

    Kruskal();
}