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DisjointSet.java
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DisjointSet.java
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import java.util.*;
import java.lang.*;
import java.io.*;
class Graph
{
int V, E; // V-> no. of vertices & E->no.of edges
Edge edge[]; // /collection of all edges
class Edge
{
int src, dest;
};
// Creates a graph with V vertices and E edges
Graph(int v,int e)
{
V = v;
E = e;
edge = new Edge[E];
for (int i=0; i<e; ++i)
edge[i] = new Edge();
}
// A utility function to find the subset of an element i
int find(int parent[], int i)
{
if (parent[i] == -1)
return i;
return find(parent, parent[i]);
}
// A utility function to do union of two subsets
void Union(int parent[], int x, int y)
{
parent[x] = y;
}
// The main function to check whether a given graph
// contains cycle or not
int isCycle( Graph graph)
{
// Allocate memory for creating V subsets
int parent[] = new int[graph.V];
// Initialize all subsets as single element sets
for (int i=0; i<graph.V; ++i)
parent[i]=-1;
// Iterate through all edges of graph, find subset of both
// vertices of every edge, if both subsets are same, then
// there is cycle in graph.
for (int i = 0; i < graph.E; ++i)
{
int x = graph.find(parent, graph.edge[i].src);
int y = graph.find(parent, graph.edge[i].dest);
if (x == y)
return 1;
graph.Union(parent, x, y);
}
return 0;
}
// Driver Method
public static void main (String[] args)
{
/* Let us create the following graph
0
| \
| \
1---2 */
int V = 3, E = 3;
Graph graph = new Graph(V, E);
// add edge 0-1
graph.edge[0].src = 0;
graph.edge[0].dest = 1;
// add edge 1-2
graph.edge[1].src = 1;
graph.edge[1].dest = 2;
// add edge 0-2
graph.edge[2].src = 0;
graph.edge[2].dest = 2;
if (graph.isCycle(graph)==1)
System.out.println( "graph contains cycle" );
else
System.out.println( "graph doesn't contain cycle" );
}
}