simple program for kruskal's algorithm in c++ code example
Example: Kruskals in c++
#include<bits/stdc++.h>
using namespace std;
typedef pair<int, int> iPair;
struct Graph
{
int V, E;
vector< pair<int, iPair> > edges;
Graph(int V, int E)
{
this->V = V;
this->E = E;
}
void addEdge(int u, int v, int w)
{
edges.push_back({w, {u, v}});
}
int kruskalMST();
};
struct DisjointSets
{
int *parent, *rnk;
int n;
DisjointSets(int n)
{
this->n = n;
parent = new int[n+1];
rnk = new int[n+1];
for (int i = 0; i <= n; i++)
{
rnk[i] = 0;
parent[i] = i;
}
}
int find(int u)
{
if (u != parent[u])
parent[u] = find(parent[u]);
return parent[u];
}
void merge(int x, int y)
{
x = find(x), y = find(y);
if (rnk[x] > rnk[y])
parent[y] = x;
else
parent[x] = y;
if (rnk[x] == rnk[y])
rnk[y]++;
}
};
int Graph::kruskalMST()
{
int mst_wt = 0;
sort(edges.begin(), edges.end());
DisjointSets ds(V);
vector< pair<int, iPair> >::iterator it;
for (it=edges.begin(); it!=edges.end(); it++)
{
int u = it->second.first;
int v = it->second.second;
int set_u = ds.find(u);
int set_v = ds.find(v);
if (set_u != set_v)
{
cout << u << " - " << v << endl;
mst_wt += it->first;
ds.merge(set_u, set_v);
}
}
return mst_wt;
}
int main()
{
int V = 9, E = 14;
Graph g(V, E);
g.addEdge(0, 1, 4);
g.addEdge(0, 7, 8);
g.addEdge(1, 2, 8);
g.addEdge(1, 7, 11);
g.addEdge(2, 3, 7);
g.addEdge(2, 8, 2);
g.addEdge(2, 5, 4);
g.addEdge(3, 4, 9);
g.addEdge(3, 5, 14);
g.addEdge(4, 5, 10);
g.addEdge(5, 6, 2);
g.addEdge(6, 7, 1);
g.addEdge(6, 8, 6);
g.addEdge(7, 8, 7);
cout << "Edges of MST are \n";
int mst_wt = g.kruskalMST();
cout << "\nWeight of MST is " << mst_wt;
return 0;
}