LeetCode:Clone Graph

题目如下：实现克隆图的算法题目链接

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:

分析：BFS或者DFS遍历图，遍历的过程中复制节点，用哈希表保存新建立的节点的地址（同时这个哈希表可以用做节点访问标志）代码如下：本文地址

 1 /**
 2  * Definition for undirected graph.
 3  * struct UndirectedGraphNode {
 4  *     int label;
 5  *     vector<UndirectedGraphNode *> neighbors;
 6  *     UndirectedGraphNode(int x) : label(x) {};
 7  * };
 8  */
 9 class Solution {
10 public:
11     UndirectedGraphNode *cloneGraph(UndirectedGraphNode *node) {
12         // IMPORTANT: Please reset any member data you declared, as
13         // the same Solution instance will be reused for each test case.
14         typedef unordered_map<int, UndirectedGraphNode *> Map;
15         if(node == NULL)return NULL;
16         Map gmap;//保存克隆图的节点的地址,顺便作为节点是否访问的标记
17         stack<UndirectedGraphNode *>gstack;
18         UndirectedGraphNode *res = new UndirectedGraphNode(node->label);
19         gmap.insert(Map::value_type(res->label, res));
20         gstack.push(node);
21         while(gstack.empty() == false)
22         {
23             UndirectedGraphNode *p = gstack.top(), *newp;
24             gstack.pop();
25             if(gmap.find(p->label) != gmap.end())//查找克隆图节点是否已经构造
26                 newp = gmap[p->label];
27             else
28             {
29                 newp = new UndirectedGraphNode(p->label);
30                 gmap.insert(Map::value_type(p->label, newp));
31             }
32             for(int i = 0; i < p->neighbors.size(); i++)
33             {
34                 UndirectedGraphNode *tmp = p->neighbors[i];
35                 if(gmap.find(tmp->label) == gmap.end())
36                 {
37                     gmap.insert(Map::value_type(tmp->label,
38                                     new UndirectedGraphNode(tmp->label)));
39                     gstack.push(tmp);
40                 }
41                 //设置克隆图节点的邻接点
42                 newp->neighbors.push_back(gmap[tmp->label]);
43             }
44         }
45         return res;
46     }
47 };

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原文地址：https://www.cnblogs.com/TenosDoIt/p/3418412.html