Kruskal.java

Kruskal.java

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+import java.util.*;
+
+class Graph {
+  class Edge implements Comparable<Edge> {
+    int src, dest, weight;
+
+    public int compareTo(Edge compareEdge) {
+      return this.weight - compareEdge.weight;
+    }
+  };
+
+  // Union
+  class subset {
+    int parent, rank;
+  };
+
+  int vertices, edges;
+  Edge edge[];
+
+  // Graph creation
+  Graph(int v, int e) {
+    vertices = v;
+    edges = e;
+    edge = new Edge[edges];
+    for (int i = 0; i < e; ++i)
+      edge[i] = new Edge();
+  }
+
+  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++;
+    }
+  }
+
+  // Applying Krushkal Algorithm
+  void KruskalAlgo() {
+    Edge result[] = new Edge[vertices];
+    int e = 0;
+    int i = 0;
+    for (i = 0; i < vertices; ++i)
+      result[i] = new Edge();
+
+    // Sorting the edges
+    Arrays.sort(edge);
+    subset subsets[] = new subset[vertices];
+    for (i = 0; i < vertices; ++i)
+      subsets[i] = new subset();
+
+    for (int v = 0; v < vertices; ++v) {
+      subsets[v].parent = v;
+      subsets[v].rank = 0;
+    }
+    i = 0;
+    while (e < vertices - 1) {
+      Edge next_edge = new Edge();
+      next_edge = 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);
+      }
+    }
+    for (i = 0; i < e; ++i)
+      System.out.println(result[i].src + " - " + result[i].dest + ": " + result[i].weight);
+  }
+
+  public static void main(String[] args) {
+    int vertices = 6; // Number of vertices
+    int edges = 8; // Number of edges
+    Graph G = new Graph(vertices, edges);
+
+    G.edge[0].src = 0;
+    G.edge[0].dest = 1;
+    G.edge[0].weight = 4;
+
+    G.edge[1].src = 0;
+    G.edge[1].dest = 2;
+    G.edge[1].weight = 4;
+
+    G.edge[2].src = 1;
+    G.edge[2].dest = 2;
+    G.edge[2].weight = 2;
+
+    G.edge[3].src = 2;
+    G.edge[3].dest = 3;
+    G.edge[3].weight = 3;
+
+    G.edge[4].src = 2;
+    G.edge[4].dest = 5;
+    G.edge[4].weight = 2;
+
+    G.edge[5].src = 2;
+    G.edge[5].dest = 4;
+    G.edge[5].weight = 4;
+
+    G.edge[6].src = 3;
+    G.edge[6].dest = 4;
+    G.edge[6].weight = 3;
+
+    G.edge[7].src = 5;
+    G.edge[7].dest = 4;
+    G.edge[7].weight = 3;
+    G.KruskalAlgo();
+  }
+}