133.克隆图

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 {
    private HashMap<Node,Node> visited = new HashMap<>();
    public Node cloneGraph(Node node) {
        if (node == null)
            return node;
		
		//如果该结点已经被访问过，从哈希表中直接取出
        if (visited.containsKey(node))
            return visited.get(node);
		
		//克隆结点
        Node temp = new Node(node.val, new ArrayList());
		//克隆结点存入哈希表
        visited.put(node, temp);
		//遍历该结点的邻居并更新克隆结点的邻居
        for (Node neighbor : node.neighbors) 
            temp.neighbors.add(cloneGraph(neighbor));

        return temp;
    }
}