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
         / \
         \_/
思路：這道題是克隆一個一模一樣的圖。使用map來保存每個節點的克隆節點，使用隊列來遍歷圖中的每個節點——遍歷的結點出隊列，沒有遍歷的結點入隊列。
然后對於每個節點的鄰居結點，在map中查找，如果有，則將其push到該節點的克隆節點的鄰居結點（也是克隆）；反之，則創建這個鄰居結點，然后作為該克隆節點的鄰居結點。

/**
 * 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;
        map<UndirectedGraphNode *,UndirectedGraphNode *> clone;
        queue<UndirectedGraphNode *> q;
        clone[node]=new UndirectedGraphNode(node->label);
        q.push(node);
        while(!q.empty())
        {
            UndirectedGraphNode *pCur=q.front();
            q.pop();
            for(int i=0;i<pCur->neighbors.size();i++)
            {
                UndirectedGraphNode *pNei=pCur->neighbors[i];
                if(clone.find(pNei)!=clone.end())
                {
                    clone[pCur]->neighbors.push_back(clone[pNei]);
                }
                else
                {
                    clone[pNei]=new UndirectedGraphNode(pNei->label);
                    clone[pCur]->neighbors.push_back(clone[pNei]);
                    q.push(pNei);
                }
            }
        }
        return clone[node];
    }
};