[LeetCode]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         / \         \_/

BFS，用hash来存储新的图和旧图的一一对应关系的点，采用BFS搜索。然后对每一个点存相邻点。

/** * Definition for undirected graph. * struct UndirectedGraphNode { *     int label; *     vector<UndirectedGraphNode *> neighbors; *     UndirectedGraphNode(int x) : label(x) {}; * }; */class Solution {public:    UndirectedGraphNode *cloneGraph(UndirectedGraphNode *node) {        unordered_map<UndirectedGraphNode * ,UndirectedGraphNode *> NodeMap;        //和克隆图之间的Map这样可以一次遍历完        queue<UndirectedGraphNode *> Qq;        if(node == NULL)            return node;        Qq.push(node);        while(!Qq.empty()){            UndirectedGraphNode *top = Qq.front();            Qq.pop();            if(NodeMap.count(top)==0){//没有节点                UndirectedGraphNode * Temp = new UndirectedGraphNode(top->label);                NodeMap[top] = Temp;            }            //保存相邻节点            for(auto it = top->neighbors.begin(); it!=top->neighbors.end(); ++it){                UndirectedGraphNode *adj = *it;                if(NodeMap.count(adj)==0){//没有该节点，创建节点，同时间也避免了环，之前遍历过的节点不会再遍历                    UndirectedGraphNode *Temp = new UndirectedGraphNode(adj->label);                    NodeMap[adj] = Temp;                    Qq.push(adj);                }                NodeMap[top]->neighbors.push_back(NodeMap[adj]); //给定字节点所有链接节点，如果有环也会保留，因为没有入队列            }        }        return NodeMap[node];    }};