LeetCode Clone Graph

题目：

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
         / \
         \_/

class Solution {
public:
	UndirectedGraphNode *cloneGraph(UndirectedGraphNode *node) {
		if (node == NULL)
			return NULL;
		queue<UndirectedGraphNode *> q;
		unordered_set<UndirectedGraphNode *> iset;
		unordered_map<UndirectedGraphNode *, UndirectedGraphNode *> table;
		q.push(node);
		while(!q.empty()) {
			UndirectedGraphNode *oldNode = q.front();
			q.pop();
			//已经处理过，不再扩展
			if (iset.find(oldNode) != iset.end())
				continue;
			iset.insert(oldNode);
			for (int i = 0; i < oldNode->neighbors.size(); i++) {
				q.push(oldNode->neighbors[i]);
			}
		}
		//创建节点以及构建新旧节点间关系
		unordered_set<UndirectedGraphNode *>::iterator it;
		for (it = iset.begin(); it != iset.end(); it++) {
			UndirectedGraphNode *oldNode = *it;
			UndirectedGraphNode *newNode = new UndirectedGraphNode(oldNode->label);
			table[oldNode] = newNode;
		}
		//创建节点与各节点之间的连接
		for (it = iset.begin(); it != iset.end(); it++) {
			UndirectedGraphNode *oldNode = *it;
			UndirectedGraphNode *newNode = table[oldNode];
			for (int i = 0; i < oldNode->neighbors.size(); i++) {
				(newNode->neighbors).push_back(table[oldNode->neighbors[i]]);	
			}
		}
		return table[node];
	}
};