题目：
Clone an undirected graph. Each node in the graph contains a label and a list of its neighbors.
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 #.
0. Connect node 0 to both nodes 1 and 2.1. Connect node 1 to node 2.2. Connect node 2 to node 2 (itself), thus forming a self-cycle.
Visually, the graph looks like the following:
1
/ / 0 --- 2
/ \_/
代码：
/** * Definition for undirected graph. * struct UndirectedGraphNode { * int label; * vector<UndirectedGraphNode *> neighbors; * UndirectedGraphNode(int x) : label(x) {}; * }; */ class Solution { public: UndirectedGraphNode *cloneGraph(UndirectedGraphNode *node) { map<UndirectedGraphNode *, UndirectedGraphNode *> copied; return Solution::dfs(copied, node); } static UndirectedGraphNode *dfs( map<UndirectedGraphNode *, UndirectedGraphNode *>& copied, UndirectedGraphNode *node) { if ( node == NULL) return NULL; if ( copied.find(node)!=copied.end() ) return copied[node]; UndirectedGraphNode *cloneNode = new UndirectedGraphNode(node->label); copied[node] = cloneNode; for ( int i=0; i<node->neighbors.size(); ++i ) { cloneNode->neighbors.push_back( Solution::dfs(copied,node->neighbors[i]) ); } return cloneNode; } };
tips：
图的深拷贝。
学到的一个技巧是如何不重复拷贝图中的node：用一个map<node *, node *>记录已经拷贝过的原图中的点以及其对应的新图中的点。
剩下的就是按照深搜模板来完成。
原文：http://www.cnblogs.com/xbf9xbf/p/4554066.html