Clone graph

/* Definition for a Node. class Node { public int val; public List<Node> neighbors; public Node() { val = 0; neighbors = new ArrayList<Node>(); } public Node(int _val) { val = _val; neighbors = new ArrayList<Node>(); } public Node(int _val, ArrayList<Node> _neighbors) { val = _val; neighbors = _neighbors; } } */ class Solution { public Node cloneGraph(Node node) { if(node ==null) return null; Map<Node,Node> map = new HashMap<>(); Node cloneNode = new Node(node.val); return dfs(node,cloneNode,map); } public Node dfs(Node a, Node b,Map<Node,Node> map){ if(map.containsKey(a)) return map.get(a); map.put(a,b); for(Node adjNode : a.neighbors){ if(!map.containsKey(adjNode)){ Node newNode = new Node(adjNode.val); b.neighbors.add(dfs(adjNode,newNode,map)); } else{ b.neighbors.add(map.get(adjNode)); } } return b; } }