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Kruskal's Algorithm.cpp
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Kruskal's Algorithm.cpp
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/*
Given an undirected, connected and weighted graph G(V, E) with V number of vertices (which are
numbered from 0 to V-1) and E number of edges.Find and print the Minimum Spanning Tree (MST)
using Kruskal's algorithm.
For printing MST follow the steps -
1. In one line, print an edge which is part of MST in the format - v1 v2 w
where, v1 and v2 are the vertices of the edge which is included in MST and
whose weight is w. And v1 <= v2 i.e. print the smaller vertex first while
printing an edge.
2. Print V-1 edges in above format in different lines.
Note : Order of different edges doesn't matter.
*/
#include <iostream>
#include <algorithm>
using namespace std;
class Edges
{
public:
long source;
long destination;
long weight;
};
bool compareWeight(Edges e1, Edges e2)
{
return (e1.weight < e2.weight);
}
long find(long v, long *parents)
{
if (v == parents[v])
return v;
return find(parents[v], parents);
}
void Union(Edges *output, Edges *input, long v, long *parents)
{
long count = 0, i = 0;
while (count < (v - 1))
{
long parentSource = find(input[i].source, parents);
long parentDestination = find(input[i].destination, parents);
if (parentSource != parentDestination)
{
output[count] = input[i];
count++;
parents[parentSource] = parents[parentDestination];
}
i++;
}
}
int main() {
long v, e;
cin >> v >> e;
Edges *input = new Edges[e];
for (long i = 0; i < e; i++)
cin >> input[i].source >> input[i].destination >> input[i].weight;
sort(input, input + e, compareWeight);
long *parents = new long[v];
for (long i = 0; i < v; i++)
parents[i] = i;
Edges *output = new Edges[v - 1];
Union(output, input, v, parents);
for (long i = 0; i < (v - 1); i++)
cout << min(output[i].source, output[i].destination) << " " << max(output[i].source, output[i].destination) << " " << output[i].weight << "\n";
delete[] input;
delete[] parents;
delete[] output;
return 0;
}