21. Clone Graph

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Clone Graph

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         /          \_/

思想： 簡單純粹的深度優先搜尋。
 

/** * Definition for undirected graph. * struct UndirectedGraphNode { *     int label; *     vector<UndirectedGraphNode *> neighbors; *     UndirectedGraphNode(int x) : label(x) {}; * }; */ typedef UndirectedGraphNode NODE; typedef pair<NODE*, NODE*> PAIR; NODE* dfs(NODE *node, unordered_map<NODE*, NODE*> &_map) {     if(_map.count(node)) return _map[node];     NODE *p = new NODE(node->label);     _map.insert(PAIR(node, p));     for(size_t i = 0; i < node->neighbors.size(); ++i) {         p->neighbors.push_back(dfs(node->neighbors[i], _map));     }     return p; } class Solution {public:    UndirectedGraphNode *cloneGraph(UndirectedGraphNode *node) {        unordered_map<NODE*, NODE*> _map;        _map[NULL] = NULL;        return dfs(node, _map);    }};

 

21. Clone Graph