我已經寫了一些代碼爲這個問題。 (python27)在Python中我的圖收縮算法行爲奇怪
圖形被表示爲與frozensets的frozenset鍵和套字典:
sample_graph = {frozenset([7]): set([frozenset([4]), frozenset([5]), frozenset([3])]), frozenset([5]): set([frozenset([7]), frozenset([2]), frozenset([1])]), frozenset([3]): set([frozenset([7]), frozenset([4]), frozenset([2]), frozenset([1])]), frozenset([6]): set([frozenset([4]), frozenset([2]), frozenset([1])]), frozenset([4]): set([frozenset([6]), frozenset([7]), frozenset([3]), frozenset([1])]), frozenset([1]): set([frozenset([6]), frozenset([4]), frozenset([5]), frozenset([2]), frozenset([3])]), frozenset([2]): set([frozenset([6]), frozenset([5]), frozenset([3]), frozenset([1])])}
輸出應該是一張圖表,其中只有兩個節點其是圖中的所有節點的frozensets。此時它會運行到KeyError。
def kargerMinCut(graph):
if len(graph) == 2:
return graph
u = random.choice(graph.keys()) # u and v are frozensets, idea is that they form
v = random.choice(list(graph[u])) # a clique in a single frozenset
for node in graph:
if node != u and node != v:
links = graph[node]
if u in links or v in links:
links.add(frozenset(tuple(u | v))) # combine u and v to form one link
links.discard(u) # delete old links to u and v
links.discard(v)
graph[node] = links
graph[u | v] = graph[u] | graph[v] # new key for u and v
del graph[u], graph[v] # u and v are no longer needed
return kargerMinCut(graph)
請修復您的縮進以匹配您正在運行的代碼。此外,如果您提供了您的輸入,預期的返回值和實際的返回值,這將有所幫助。 – chepner 2012-07-05 20:17:20
縮進僅在def的第一行被違反。我會添加示例圖形輸入,但它是隨機算法,所以我無法確切知道輸出是什麼。 – AndrewSokolowski 2012-07-05 20:34:16
@AndrewSokolowski在這種情況下,我會製作一個小的演示圖並選擇具體的'u'和'v'。先從一個你知道會發生什麼的例子開始,以幫助你決定你的代碼是否按照預期工作:「有一天,愛麗絲來到路邊的一個叉子上,在樹上看到一隻柴郡貓。我拿?*她問。*你想去哪兒?*是他的回答。*我不知道*,愛麗絲回答。*然後*,說貓,*沒關係。*「:) – user 2012-07-05 20:52:25