Clone Graph

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 #.

1. First node is labeled as 0. Connect node 0 to both nodes 1 and 2.
2. Second node is labeled as 1. Connect node 1 to node 2.
3. 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
         / \
         \_/

思考： 实现深度复制，但会出现环形，避免每个节点多次复制，可以将已经复制过的节点进行保存，label是唯一确定的，所以用label和node联系起来，然后进行递归即可。
java代码：

1. Map<Integer,UndirectedGraphNode> mp = new HashMap<Integer,UndirectedGraphNode>();
2. UndirectedGraphNode helper(UndirectedGraphNode node,Map<Integer,UndirectedGraphNode> mp) {
3. if(node==null) return null;
4. if(mp.containsKey(node.label)) return mp.get(node.label);
5. UndirectedGraphNode new_node = new UndirectedGraphNode(node.label);
6. mp.put(node.label,new_node);
7. for(int i=0;i<node.neighbors.size();i++) {
8. UndirectedGraphNode child = cloneGraph(node.neighbors.get(i));
9. new_node.neighbors.add(child);
10. }
11. return new_node;
12. }
13. public UndirectedGraphNode cloneGraph(UndirectedGraphNode node) {
14. if(node == null) return null;
15. UndirectedGraphNode new_node = helper(node,mp);
16. return new_node;
17. }

C++代码：

1. UndirectedGraphNode *cloneGraph(UndirectedGraphNode *node) {
2. UndirectedGraphNode *root =NULL;
3. if(node==NULL) return root;
4. unordered_map<int,UndirectedGraphNode *> track;
5. root = cloneGraph(node,track);
6. return root;
7. }
8. UndirectedGraphNode *cloneGraph(UndirectedGraphNode *node, unordered_map<int,UndirectedGraphNode *> & track) {
9. if(!node) return NULL;
10. if(track.count(node->label)) return track[node->label];
11. UndirectedGraphNode *root = new UndirectedGraphNode(node->label);
12. root->neighbors.resize(node->neighbors.size());
13. //root->label=node->label;
14. track[node->label]=root;
15. for(int i=0;i<node->neighbors.size();i++) {
16. root->neighbors[i] = cloneGraph(node->neighbors[i],track);
17. }
18. return root;
19. }