Java -Solution- To find Articulation points in a graph

Find Articulation points in a graph so that we can divided the graph into two connected graphs.

Solution:

import java.util.Iterator;
import java.util.LinkedList;

public class Graph {

private int vertices; ;
private LinkedList<Integer> graph[];

private int time;

static final int NIL = -1;
int visited[];

//keep the distance from origin
private int distance[];

//keep the record of lowest distance of subtree
private int lowestAdj[];

//track the parent of vertices
private int parent[];

//articulate points store
private int articulatePoints[];


public Graph(int vertices){
this.vertices = vertices;
graph = new LinkedList[vertices];
visited = new int[vertices];
this.parent = new int[vertices];
this.articulatePoints = new int[vertices];
this.lowestAdj = new int[vertices];
this.distance = new int[vertices];
this.initialize();
}

private void initialize(){
for(int i = 0 ; i < this.vertices ; i++){
graph[i] = new LinkedList<Integer>();
}
}

public void addEdge(int u , int v){
graph[u].add(v);
graph[v].add(u);
}

private void articulateUtil(int u){

int children  = 0 ;

this.visited[u] = 1;

this.distance[u] = this.lowestAdj[u] = ++time;

Iterator<Integer> items = this.graph[u].iterator();

while(items.hasNext()){

int item = items.next();

if(this.visited[item] == 0){
children++;
this.parent[item] = u;
articulateUtil(item);

lowestAdj[u] = Math.min(lowestAdj[u], lowestAdj[item]);

//we need to find two conditions one for parent and another for back edge

if(parent[u] == NIL && children > 1){
this.articulatePoints[u] = 1;
}
else if(this.parent[u] != NIL && this.distance[u] <= this.lowestAdj[item]){
this.articulatePoints[u] = 1;
}

}

else if( item != parent[u] ){
lowestAdj[u] = Math.min(distance[item], lowestAdj[u]);
}
}



}

public void findArticulatePoint(){

for(int i = 0 ; i < this.vertices ; i++){
this.parent[i] = NIL;
}
for(int i = 0 ; i < this.vertices ; i++){
if(this.visited[i] == 0){
this.articulateUtil(i);
}
}
for(int i = 0 ; i < this.vertices ; i++){
if(this.articulatePoints[i] == 1){
System.out.println("This is articulate points " + i);
}
}
}

public static void main(String [] args){
        Graph graph = new Graph(5);
        graph.addEdge(1, 0);
        graph.addEdge(0, 2);
        graph.addEdge(2, 1);
        graph.addEdge(0, 3);
        graph.addEdge(3, 4);
        graph.findArticulatePoint();

}

}

Reference :- http://www.geeksforgeeks.org/articulation-points-or-cut-vertices-in-a-graph/