Given a reference of a node in a connected undirected graph.
+ +Return a deep copy (clone) of the graph.
+ +Each node in the graph contains a value (int) and a list (List[Node]) of its neighbors.
+class Node {
+ public int val;
+ public List<Node> neighbors;
+}
+
+
++ +
Test case format:
+ +For simplicity, each node's value is the same as the node's index (1-indexed). For example, the first node with val == 1, the second node with val == 2, and so on. The graph is represented in the test case using an adjacency list.
An adjacency list is a collection of unordered lists used to represent a finite graph. Each list describes the set of neighbors of a node in the graph.
+ +The given node will always be the first node with val = 1. You must return the copy of the given node as a reference to the cloned graph.
+
Example 1:
+
++Input: adjList = [[2,4],[1,3],[2,4],[1,3]] +Output: [[2,4],[1,3],[2,4],[1,3]] +Explanation: There are 4 nodes in the graph. +1st node (val = 1)'s neighbors are 2nd node (val = 2) and 4th node (val = 4). +2nd node (val = 2)'s neighbors are 1st node (val = 1) and 3rd node (val = 3). +3rd node (val = 3)'s neighbors are 2nd node (val = 2) and 4th node (val = 4). +4th node (val = 4)'s neighbors are 1st node (val = 1) and 3rd node (val = 3). ++ +
Example 2:
+
++Input: adjList = [[]] +Output: [[]] +Explanation: Note that the input contains one empty list. The graph consists of only one node with val = 1 and it does not have any neighbors. ++ +
Example 3:
+ ++Input: adjList = [] +Output: [] +Explanation: This an empty graph, it does not have any nodes. ++ +
+
Constraints:
+ +[0, 100].1 <= Node.val <= 100Node.val is unique for each node.