133. Clone Graph

图的遍历，也就是bfs，区别在于，每一个点的左右节点不是预先知道的，是要创建的时候加进去

 

    public UndirectedGraphNode cloneGraph(UndirectedGraphNode node) {
        if(node == null) {
            return null;
        }
        Queue<UndirectedGraphNode> queue = new LinkedList<UndirectedGraphNode>();
        UndirectedGraphNode newNode = new UndirectedGraphNode(node.label);
        queue.offer(node);
        Map<UndirectedGraphNode, UndirectedGraphNode> map = new HashMap<UndirectedGraphNode, UndirectedGraphNode>();
        map.put(node, newNode);
        while(!queue.isEmpty()) {
            UndirectedGraphNode cur = queue.poll();
            for(UndirectedGraphNode neighbor: cur.neighbors) {
                UndirectedGraphNode newNeighbor = map.get(neighbor);
                if(!map.containsKey(neighbor)) {
                    newNeighbor = new UndirectedGraphNode(neighbor.label);
                    map.put(neighbor, newNeighbor);
                    queue.add(neighbor);
                }
                map.get(cur).neighbors.add(newNeighbor);
            }
        }
        return newNode;
    }