Clone Graph.py

'''
 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 #.

    First node is labeled as 0. Connect node 0 to both nodes 1 and 2.
    Second node is labeled as 1. Connect node 1 to node 2.
    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
         / \
         \_/

'''

# Definition for a undirected graph node
# class UndirectedGraphNode:
#     def __init__(self, x):
#         self.label = x
#         self.neighbors = []

class Solution:
    # @param node, a undirected graph node
    # @return a undirected graph node
    def cloneGraph(self, node):
        if not node:
            return None
        
        dic = {}
        mirror = UndirectedGraphNode(node.label)
        dic[node] = mirror
        
        vec = [node]
        visited = set([node])
        while vec:
            tmp = vec.pop()
            for neighbor in tmp.neighbors:
                if neighbor not in dic:
                    mirror = UndirectedGraphNode(neighbor.label)
                    dic[neighbor] = mirror
                    
                dic[tmp].neighbors.append(dic[neighbor])
                
                if neighbor not in visited:
                    visited.add(neighbor)
                    vec.append(neighbor)
                    
        return dic[node]