kruskal.cpp

#include <iostream>
#include <vector>
#include <utility>
#include <algorithm>
 
using namespace std;
const int MAX = 1e4 + 5;
int id[MAX], nodes, edges;
pair <long long, pair<int, int> > p[MAX];
 
void initialize()
{
    for(int i = 0;i < MAX;++i)
        id[i] = i;
}
 
int root(int x)
{
    if(x==id[x])
    	return id[x];
	return id[x] = root(id[x]);
}
 
void union1(int x, int y)
{
    int p = root(x);
    int q = root(y);
    id[p] = id[q];
}
 
long long kruskal(pair<long long, pair<int, int> > p[])
{
    int x, y;
    long long cost, minimumCost = 0;
    for(int i = 0;i < edges;++i)
    {
        // Selecting edges one by one in increasing order from the beginning
        x = p[i].second.first;
        y = p[i].second.second;
        cost = p[i].first;
        // Check if the selected edge is creating a cycle or not
        if(root(x) != root(y))
        {
            minimumCost += cost;
            union1(x, y);
        }    
    }
    return minimumCost;
}
 
int main()
{
    int x, y;
    long long weight, cost, minimumCost;
    initialize();
    cin >> nodes >> edges;
    for(int i = 0;i < edges;++i)
    {
        cin >> x >> y >> weight;
        p[i] = make_pair(weight, make_pair(x, y));
    }
    // Sort the edges in the ascending order
    sort(p, p + edges);
    minimumCost = kruskal(p);
    cout << minimumCost << endl;
    return 0;
}