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 #.

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
         / \
         \_/

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

 /**
  * Definition for undirected graph.
  * struct UndirectedGraphNode {
  *     int label;
  *     vector<UndirectedGraphNode *> neighbors;
  *     UndirectedGraphNode(int x) : label(x) {};
  * };
  */
 class Solution {
 public:
     UndirectedGraphNode *cloneGraph(UndirectedGraphNode *node) {
         // IMPORTANT: Please reset any member data you declared, as
         // the same Solution instance will be reused for each test case.
         typedef unordered_map<int, UndirectedGraphNode *> Map;
         if(node == NULL)return NULL;
         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
         stack<UndirectedGraphNode *>gstack;
         UndirectedGraphNode *res = new UndirectedGraphNode(node->label);
         gmap.insert(Map::value_type(res->label, res));
         gstack.push(node);
         while(gstack.empty() == false)
         {
             UndirectedGraphNode *p = gstack.top(), *newp;
             gstack.pop();
             if(gmap.find(p->label) != gmap.end())//查找克隆图节点是否已经构造
                 newp = gmap[p->label];
             else
             {
                 newp = new UndirectedGraphNode(p->label);
                 gmap.insert(Map::value_type(p->label, newp));
             }
             for(int i = ; i < p->neighbors.size(); i++)
             {
                 UndirectedGraphNode *tmp = p->neighbors[i];
                 if(gmap.find(tmp->label) == gmap.end())
                 {
                     gmap.insert(Map::value_type(tmp->label,
                                     new UndirectedGraphNode(tmp->label)));
                     gstack.push(tmp);
                 }
                 //设置克隆图节点的邻接点
                 newp->neighbors.push_back(gmap[tmp->label]);
             }
         }
         return res;
     }
 };

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