描述
Clone an undirected graph. Each node in the graph contains a label and a list of its neighbors. Nodes are labeled uniquely.
You need to return a deep copied graph, which has the same structure as the original graph, and any changes to the new graph will not have any effect on the original graph.
You need return the node with the same label as the input node.
說明
How we serialize an undirected graph: http://www.lintcode.com/help/graph/
樣例
Example1
Input:
{1,2,4#2,1,4#4,1,2}
Output:
{1,2,4#2,1,4#4,1,2}
Explanation:
1------2
\ |
\ |
\ |
\ |
4
同時，類的定義是：
"""
class UndirectedGraphNode:
def __init__(self, x):
self.label = x
self.neighbors = []
"""
Note： 實話說，第一次遇到類似的題目。複製Python的list和dict等時，a=[1,2,3]; b= a; b.append(4); 的時候，a和b都爲[1,2,3,4]。這就是淺複製。要想在數據結構上實現深複製，需要把數據結構的各個部分單獨複製。本題中，需要把label和neighbor分別複製。
（本題解參考九章）
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from collections import deque
"""
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):
root = node #哪個點是入口，待會仍然從這個點開始
if node is None:
return node
# write your code here
nodes = self.getnodes(node)
mapping = {}
for node in nodes:
mapping[node] = UndirectedGraphNode(node.label)
for node in nodes:
#new_node = mapping[node]
for neighbor in node.neighbors:
#new_neighbor = mapping[neighbor]
#new_node.neighbors.append(new_neighbor)
mapping[node].neighbors.append(mapping[neighbor])
return mapping[root]
def getnodes(self,node):
queue = deque([node])
result = set([node])
while(queue):
head = queue.popleft()
for neighbor in head.neighbors:
if(neighbor not in result):
result.add(neighbor)
queue.append(neighbor)
return result