133. 克隆图

/*
// 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,Node>();
        ArrayList<Node> nodes=getNodes(node);
        //copy node
        for(Node n:nodes){
            map.put(n,new Node(n.val));
        }
        //copy neighbors
        for(Node n:nodes){
            Node newNode=map.get(n);
            for(Node neighbor:n.neighbors){
                Node newNeighbor=map.get(neighbor);
                newNode.neighbors.add(newNeighbor);
            }
        }
        return map.get(node);
    }
    public ArrayList<Node> getNodes(Node node){
        //这里使用队列queue和set实现链表
        Queue<Node> queue=new LinkedList<Node>();
        HashSet<Node> set=new HashSet<Node>();
        queue.add(node);
        set.add(node);
        while(!queue.isEmpty()){
            Node head=queue.poll();
            for(Node neighbor:head.neighbors){
                if(!set.contains(neighbor)){
                    set.add(neighbor);
                    queue.add(neighbor);
                }
            }
        }
        return new ArrayList(set);
    }
}