[LeetCode] Clone Graph

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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         /          \_/
思路：用map儲存建立的新的結點，其中key是結點的label值，value是結點的指標值。

/** * Definition for undirected graph. * struct UndirectedGraphNode { *     int label; *     vector<UndirectedGraphNode *> neighbors; *     UndirectedGraphNode(int x) : label(x) {}; * }; */class Solution {public:    UndirectedGraphNode *cloneGraph(UndirectedGraphNode *node) {        if(node==NULL)            return NULL;        UndirectedGraphNode *pnode = node;        UndirectedGraphNode *head = new UndirectedGraphNode(node->label);        UndirectedGraphNode *p = head;        map<int,UndirectedGraphNode *> labelAndNode;        labelAndNode[head->label] = head;        pNodeNeighbors(pnode,p,labelAndNode);        return head;    }private:    void pNodeNeighbors(UndirectedGraphNode *&pnode,UndirectedGraphNode *&p,map<int,UndirectedGraphNode *> &labelAndNode)    {        int num = pnode->neighbors.size();        UndirectedGraphNode *pnew ;        for(int i = 0;i<num;i++)        {            if(labelAndNode.count(pnode->neighbors[i]->label)==0)            {               pnew = new UndirectedGraphNode(pnode->neighbors[i]->label);               labelAndNode[pnode->neighbors[i]->label] = pnew;               p->neighbors.push_back(pnew);               pNodeNeighbors(pnode->neighbors[i],p->neighbors[i],labelAndNode);            }            else            {              pnew =  labelAndNode[pnode->neighbors[i]->label];              p->neighbors.push_back(pnew);            }                }            }};