Clone Graph

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tab: English
 
<p>Given a reference of a node in a <strong><a href="https://en.wikipedia.org/wiki/Connectivity_(graph_theory)#Connected_graph" target="_blank">connected</a></strong> undirected graph.</p>
 
<p>Return a <a href="https://en.wikipedia.org/wiki/Object_copying#Deep_copy" target="_blank"><strong>deep copy</strong></a> (clone) of the graph.</p>
 
<p>Each node in the graph contains a value (<code>int</code>) and a list (<code>List[Node]</code>) of its neighbors.</p>
 
<pre>
class Node {
    public int val;
    public List&lt;Node&gt; neighbors;
}
</pre>
 
<p>&nbsp;</p>
 
<p><strong>Test case format:</strong></p>
 
<p>For simplicity, each node&#39;s value is the same as the node&#39;s index (1-indexed). For example, the first node with <code>val == 1</code>, the second node with <code>val == 2</code>, and so on. The graph is represented in the test case using an adjacency list.</p>
 
<p><b>An adjacency list</b> is a collection of unordered <b>lists</b> used to represent a finite graph. Each list describes the set of neighbors of a node in the graph.</p>
 
<p>The given node will always be the first node with <code>val = 1</code>. You must return the <strong>copy of the given node</strong> as a reference to the cloned graph.</p>
 
<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>
<img alt="" src="https://assets.leetcode.com/uploads/2019/11/04/133_clone_graph_question.png" style="width: 454px; height: 500px;" />
<pre>
<strong>Input:</strong> adjList = [[2,4],[1,3],[2,4],[1,3]]
<strong>Output:</strong> [[2,4],[1,3],[2,4],[1,3]]
<strong>Explanation:</strong> There are 4 nodes in the graph.
1st node (val = 1)&#39;s neighbors are 2nd node (val = 2) and 4th node (val = 4).
2nd node (val = 2)&#39;s neighbors are 1st node (val = 1) and 3rd node (val = 3).
3rd node (val = 3)&#39;s neighbors are 2nd node (val = 2) and 4th node (val = 4).
4th node (val = 4)&#39;s neighbors are 1st node (val = 1) and 3rd node (val = 3).
</pre>
 
<p><strong class="example">Example 2:</strong></p>
<img alt="" src="https://assets.leetcode.com/uploads/2020/01/07/graph.png" style="width: 163px; height: 148px;" />
<pre>
<strong>Input:</strong> adjList = [[]]
<strong>Output:</strong> [[]]
<strong>Explanation:</strong> 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.
</pre>
 
<p><strong class="example">Example 3:</strong></p>
 
<pre>
<strong>Input:</strong> adjList = []
<strong>Output:</strong> []
<strong>Explanation:</strong> This an empty graph, it does not have any nodes.
</pre>
 
<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>
 
<ul>
	<li>The number of nodes in the graph is in the range <code>[0, 100]</code>.</li>
	<li><code>1 &lt;= Node.val &lt;= 100</code></li>
	<li><code>Node.val</code> is unique for each node.</li>
	<li>There are no repeated edges and no self-loops in the graph.</li>
	<li>The Graph is connected and all nodes can be visited starting from the given node.</li>
</ul>
 
 
 
---
 
[submissions](https://leetcode.com/problems/clone-graph/submissions/) | [solutions](https://leetcode.com/problems/clone-graph/solutions/)
 
 
tab: 中文
 
<p>给你无向&nbsp;<strong><a href="https://baike.baidu.com/item/连通图/6460995?fr=aladdin" target="_blank">连通</a>&nbsp;</strong>图中一个节点的引用，请你返回该图的&nbsp;<a href="https://baike.baidu.com/item/深拷贝/22785317?fr=aladdin" target="_blank"><strong>深拷贝</strong></a>（克隆）。</p>
 
<p>图中的每个节点都包含它的值 <code>val</code>（<code>int</code>） 和其邻居的列表（<code>list[Node]</code>）。</p>
 
<pre>
class Node {
    public int val;
    public List&lt;Node&gt; neighbors;
}</pre>
 
<p>&nbsp;</p>
 
<p><strong>测试用例格式：</strong></p>
 
<p>简单起见，每个节点的值都和它的索引相同。例如，第一个节点值为 1（<code>val = 1</code>），第二个节点值为 2（<code>val = 2</code>），以此类推。该图在测试用例中使用邻接列表表示。</p>
 
<p><strong>邻接列表</strong> 是用于表示有限图的无序列表的集合。每个列表都描述了图中节点的邻居集。</p>
 
<p>给定节点将始终是图中的第一个节点（值为 1）。你必须将&nbsp;<strong>给定节点的拷贝&nbsp;</strong>作为对克隆图的引用返回。</p>
 
<p>&nbsp;</p>
 
<p><strong>示例 1：</strong></p>
 
<p><img alt="" src="https://assets.leetcode-cn.com/aliyun-lc-upload/uploads/2020/02/01/133_clone_graph_question.png" style="height: 500px; width: 500px;" /></p>
 
<pre>
<strong>输入：</strong>adjList = [[2,4],[1,3],[2,4],[1,3]]
<strong>输出：</strong>[[2,4],[1,3],[2,4],[1,3]]
<strong>解释：
</strong>图中有 4 个节点。
节点 1 的值是 1，它有两个邻居：节点 2 和 4 。
节点 2 的值是 2，它有两个邻居：节点 1 和 3 。
节点 3 的值是 3，它有两个邻居：节点 2 和 4 。
节点 4 的值是 4，它有两个邻居：节点 1 和 3 。
</pre>
 
<p><strong>示例 2：</strong></p>
 
<p><img alt="" src="https://assets.leetcode-cn.com/aliyun-lc-upload/uploads/2020/02/01/graph.png" style="height: 148px; width: 163px;" /></p>
 
<pre>
<strong>输入：</strong>adjList = [[]]
<strong>输出：</strong>[[]]
<strong>解释：</strong>输入包含一个空列表。该图仅仅只有一个值为 1 的节点，它没有任何邻居。
</pre>
 
<p><strong>示例 3：</strong></p>
 
<pre>
<strong>输入：</strong>adjList = []
<strong>输出：</strong>[]
<strong>解释：</strong>这个图是空的，它不含任何节点。
</pre>
 
<p>&nbsp;</p>
 
<p><strong>提示：</strong></p>
 
<ul>
	<li>这张图中的节点数在 <code>[0, 100]</code>&nbsp;之间。</li>
	<li><code>1 &lt;= Node.val &lt;= 100</code></li>
	<li>每个节点值&nbsp;<code>Node.val</code> 都是唯一的，</li>
	<li>图中没有重复的边，也没有自环。</li>
	<li>图是连通图，你可以从给定节点访问到所有节点。</li>
</ul>
 
 
 
---
 
[提交记录](https://leetcode.cn/problems/clone-graph/submissions/) | [题解](https://leetcode.cn/problems/clone-graph/solution/)

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