Medium：Clone Graph

Clone Graph

目标：克隆一个无向图

Clone an undirected graph. Each node in the graph contains a label and a list of its neighbors.
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.

★★★

在solution里添加一个map<UndirectedGraphNode *, UndirectedGraphNode *> m来保存克隆图（Key 为节点，Value 为该节点的邻接节点）。用DFS算法遍历全图，若当前节点已在克隆图中，则返回克隆图中的该节点，否则创立新节点加入克隆图中，并添加其所有邻接节点。

程序如下：

class Solution {  
public:  
    UndirectedGraphNode *cloneGraph(UndirectedGraphNode *node) {  
        if(!node) 
            return NULL;  
        if(m.count(node)) 
            return m[node];  
        UndirectedGraphNode *nodeClone = new UndirectedGraphNode(node->label);
        m[node] = nodeClone;
        for(int i=0;i<node->neighbors.size();i++)  
        {
            UndirectedGraphNode *temp = cloneGraph(node->neighbors[i]);
            if(temp != NULL)
                nodeClone->neighbors.push_back(temp);
        }
        return nodeClone;
    }  
private:  
    map<UndirectedGraphNode *, UndirectedGraphNode *> m;  
};