clone graph@leetcode

刷题必备书籍：Cracking the Coding Interview: 150 Programming Questions and Solutions 

简历：The Google Resume: How to Prepare for a Career and Land a Job at Apple, Microsoft, Google, or any Top Tech Company
算法学习书籍：Introduction to Algorithms
编程珠玑：Programming Pearls (2nd Edition)
C++ 学习：The C++ Programming Language, 4th Edition
经典操作系统书籍，龙书：Operating System Concepts
创业：The Start-up of You: Adapt to the Future, Invest in Yourself, and Transform Your Career

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 from 0 to N - 1, where N is the total nodes in the graph.

We use # as a separator for each node, and , as a separator for each neighbor of the node.

As an example, consider the serialized graph {1,2#2#2}.

The graph has a total of three nodes, and therefore contains three parts as separated by #.

1. Connect node 0 to both nodes 1 and 2.
2. Connect node 1 to node 2.
3. Connect node 2 to node 2 (itself), thus forming a self-cycle.

Visually, the graph looks like the following:

       1
      / \
     /   \
    0 --- 2
         / \
         \_/

这题不难，就是很烦人，主要是要搞清楚新建立的结点，指针，存放在HASHMAP和QUEUE里的分别是什么，对应清楚就好。HASHMAP用来MARK已经VSITED的NODE，QUEUE用来做BFS来CLONE GRAPH。