Merge pull request deutranium#82 from arushimgupta/kruskals

Add Kruskals in java

Author: deutranium

ClassicalAlgos/Kruskal's_algorithm/Kruskals.java

@@ -0,0 +1,112 @@
+// Find MST of given graph
+import java.util.*; 
+import java.lang.*; 
+import java.io.*; 
+
+class Graph 
+{  
+	class Edge implements Comparable<Edge> 
+	{ 
+		int src, dest, weight; 
+		public int compareTo(Edge compareEdge) 
+		{ 
+			return this.weight-compareEdge.weight; 
+		} 
+	}; 
+	class subset 
+	{ 
+		int parent, rank; 
+	}; 
+
+	int V, E;  
+	Edge edge[]; 
+	Graph(int v, int e) 
+	{ 
+		V = v; 
+		E = e; 
+		edge = new Edge[E]; 
+		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++; 
+		} 
+	} 
+
+	void KruskalMST() 
+	{ 
+		Edge result[] = new Edge[V]; 
+		int e = 0; 
+		int i = 0; 
+		for (i=0; i<V; ++i) 
+			result[i] = new Edge();  
+		Arrays.sort(edge);  
+		subset subsets[] = new subset[V]; 
+		for(i=0; i<V; ++i) 
+			subsets[i]=new subset(); 
+		for (int v = 0; v < V; ++v) 
+		{ 
+			subsets[v].parent = v; 
+			subsets[v].rank = 0; 
+		} 
+
+		i = 0; 
+		while (e < V - 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 V = 4;  
+		int E = 5;
+		Graph graph = new Graph(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.KruskalMST(); 
+	} 
+}