data-structure/kruskals.cpp at master · Gauri0799/data-structure · GitHub

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#include <bits/stdc++.h>
#include<iostream>
using namespace std;
class Edge
{
    public:
    int src, dest, weight;
};
class Graph
{
    public:
    int V, E;
    Edge* edge;
};
Graph* createGraph(int V, int E)
{
    Graph* graph = new Graph;
    graph->V = V;
    graph->E = E;

    graph->edge = new Edge[E];

    return graph;
}
class subset
{
    public:
    int parent;
    int rank;
};
int find(subset subsets[], int i)
{
    if (subsets[i].parent != i)
        subsets[i].parent = find(subsets, subsets[i].parent);

    return subsets[i].parent;
}
void Union(subset subsets[], int x, int y)
{
    int xroot = find(subsets, x);
    int yroot = find(subsets, y);
    if (subsets[xroot].rank < subsets[yroot].rank)
        subsets[xroot].parent = yroot;
    else if (subsets[xroot].rank > subsets[yroot].rank)
        subsets[yroot].parent = xroot;
    else
    {
        subsets[yroot].parent = xroot;
        subsets[xroot].rank++;
    }
}
int myComp(const void* a, const void* b)
{
    Edge* a1 = (Edge*)a;
    Edge* b1 = (Edge*)b;
    return a1->weight > b1->weight;
}
void KruskalMST(Graph* graph)
{
    int V = graph->V;
    Edge result[V];
    int e = 0;
    int i = 0;
    qsort(graph->edge, graph->E, sizeof(graph->edge[0]), myComp);
    subset *subsets = new subset[( V * sizeof(subset) )];
    for (int v = 0; v < V; ++v)
    {
        subsets[v].parent = v;
        subsets[v].rank = 0;
    }
    while (e < V - 1 && i < graph->E)
    {
        Edge next_edge = graph->edge[i++];
        int x = find(subsets, next_edge.src);
        int y = find(subsets, next_edge.dest);
        if (x != y)
        {
            result[e++] = next_edge;
            Union(subsets, x, y);
        }
    }
    cout<<"Following are the edges in the constructed MST\n";
    for (i = 0; i < e; ++i)
        cout<<result[i].src<<" -- "<<result[i].dest<<" == "<<result[i].weight<<endl;
    return;
}
int main()
{
    /* Let us create following weighted graph
            10
        0--------1
        | \ |
    6| 5\ |15
        | \ |
        2--------3
            4 */
    int V = 4;
    int E = 5;
    Graph* graph = createGraph(V, E);

    graph->edge[0].src = 0;
    graph->edge[0].dest = 1;
    graph->edge[0].weight = 10;

    graph->edge[1].src = 0;
    graph->edge[1].dest = 2;
    graph->edge[1].weight = 6;

    graph->edge[2].src = 0;
    graph->edge[2].dest = 3;
    graph->edge[2].weight = 5;

    graph->edge[3].src = 1;
    graph->edge[3].dest = 3;
    graph->edge[3].weight = 15;

    graph->edge[4].src = 2;
    graph->edge[4].dest = 3;
    graph->edge[4].weight = 4;
    KruskalMST(graph);
    return 0;
}