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 node0
to both nodes1
and2
. - Second node is labeled as
1
. Connect node1
to node2
. - Third node is labeled as
2
. Connect node2
to node2
(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
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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