【Leetcode】 Clone Graph

题目链接：https://leetcode.com/problems/clone-graph/

题目：

Clone an undirected graph. Each node in the graph contains a

label

and a list of its

neighbors

.

OJ's undirected graph serialization:

Nodes are labeled uniquely.
We use

#

as a separator for each node, and

,

as
a separator for node label and each neighbor of the node.

As an example, consider the serialized graph

{0,1,2#1,2#2,2}

.

The graph has a total of three nodes, and therefore contains three parts as separated by

#

.

First node is labeled as

0

. Connect node

0

to
both nodes

1

and

2

.
Second node is labeled as

1

. Connect node

1

to
node

2

.
Third node is labeled as

2

. Connect node

2

to
node

2

(itself), thus forming a self-cycle.

Visually, the graph looks like the following:

1
/ \
/   \
0 --- 2
/ \
\_/

思路：

BFS/DFS ，因为标签唯一，所以用Map保存对应关系，这里用dfs递归拷贝新节点。

算法：

Map<Integer, UndirectedGraphNode> sets = new HashMap<Integer, UndirectedGraphNode>();
public UndirectedGraphNode cloneGraph(UndirectedGraphNode node) {
if(node == null)
return null;
if(sets.containsKey(node.label))
return sets.get(node.label);

UndirectedGraphNode newNode = new UndirectedGraphNode(node.label);
sets.put(newNode.label, newNode);
for (UndirectedGraphNode neighbor : node.neighbors) {
newNode.neighbors.add(cloneGraph(neighbor));
}
return newNode;
}