CloneGraph

/***************************************************************************
  Class for graph node is as follows:
  class graphNode {
      public int data;
      public ArrayList<graphNode> neighbours;
      graphNode() {
          data = 0;
          neighbours = new ArrayList<graphNode>();
      }
      graphNode(int val) {
          data = val;
          neighbours = new ArrayList<graphNode>();
      }
      graphNode(int val, ArrayList<graphNode> neighbours) {
          data = val;
          this.neighbours = neighbours;
      }
    }
******************************************************************************/
import java.util.*;
public class Solution {
    public static graphNode cloneGraph(graphNode node) {
        
        return cloneGraphDFSHelper(node,new HashMap<graphNode,graphNode>());
    }
    private static graphNode cloneGraphDFSHelper(graphNode cur, HashMap<graphNode, graphNode> visited) {
        if (cur == null) {
            return null;
        }
        if (visited.containsKey(cur)) {
            return visited.get(cur);
        }

        graphNode newNode = new graphNode(cur.data);
        visited.put(cur, newNode);

        for (graphNode n : cur.neighbours) {
            newNode.neighbours.add(cloneGraphDFSHelper(n, visited));
        }

        return newNode;
    }
}