Example 1: kruskal's algorithm
#include<bits/stdc++.h>
using namespace std;
int main()
{
int n = 9;
int mat[9][9] = {
{100,4,100,100,100,100,100,8,100},
{4,100,8,100,100,100,100,100,100},
{100,8,100,7,100,4,100,100,2},
{100,100,7,100,9,14,100,100,100},
{100,100,100,9,100,10,100,100,100},
{100,100,4,14,10,100,2,100,100},
{100,100,100,100,100,2,100,1,6},
{8,100,100,100,100,100,1,100,7},
{100,100,2,100,100,100,6,7,100}};
int parent[n];
int edges[100][3];
int count = 0;
for(int i=0;i<n;i++)
for(int j=i;j<n;j++)
{
if(mat[i][j] != 100)
{
edges[count][0] = i;
edges[count][1] = j;
edges[count++][2] = mat[i][j];
}
}
for(int i=0;i<count-1;i++)
for(int j=0;j<count-i-1;j++)
if(edges[j][2] > edges[j+1][2])
{
int t1=edges[j][0], t2=edges[j][1], t3=edges[j][2];
edges[j][0] = edges[j+1][0];
edges[j][1] = edges[j+1][1];
edges[j][2] = edges[j+1][2];
edges[j+1][0] = t1;
edges[j+1][1] = t2;
edges[j+1][2] = t3;
}
int mst[n-1][2];
int mstVal = 0;
int l = 0;
cout<<endl;
for(int i=0;i<n;i++)
parent[i] = -1;
cout<<endl;
for(int i=0;i<count;i++)
{
if((parent[edges[i][0]] == -1 && parent[edges[i][1]] == -1))
{
parent[edges[i][0]] = edges[i][0];
parent[edges[i][1]] = edges[i][0];
mst[l][0] = edges[i][0];
mst[l++][1] = edges[i][1];
mstVal += edges[i][2];
}
else if((parent[edges[i][0]] == -1 && parent[edges[i][1]] != -1))
{
parent[edges[i][0]] = parent[edges[i][1]];
mst[l][0] = edges[i][1];
mst[l++][1] = edges[i][0];
mstVal += edges[i][2];
}
else if((parent[edges[i][0]] != -1 && parent[edges[i][1]] == -1))
{
parent[edges[i][1]] = parent[edges[i][0]];
mst[l][0] = edges[i][0];
mst[l++][1] = edges[i][1];
mstVal += edges[i][2];
}
else if(parent[edges[i][0]] != -1 && parent[edges[i][1]] != -1 && parent[edges[i][0]] != parent[edges[i][1]])
{
int p = parent[edges[i][1]];
for(int j=0;j<n;j++)
if(parent[j] == p)
parent[j] = parent[edges[i][0]];
mst[l][0] = edges[i][0];
mst[l++][1] = edges[i][1];
mstVal += edges[i][2];
}
}
for(int i=0;i<l;i++)
cout<<mst[i][0]<<" -> "<<mst[i][1]<<endl;
cout<<endl;
cout<<mstVal<<endl;
return(0);
}
Example 2: kruskal's algorithm c++ hackerearth
#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)
{
while(id[x] != x)
{
id[x] = id[id[x]];
x = id[x];
}
return 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)
{
x = p[i].second.first;
y = p[i].second.second;
cost = p[i].first;
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(p, p + edges);
minimumCost = kruskal(p);
cout << minimumCost << endl;
return 0;
}
Example 3: 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;
}