# Python stack overflow

• The last test case is too big for a recursive solution to get accepted.

``````import collections
class Solution(object):
def sequenceReconstruction(self, org, seqs):
"""
:type org: List[int]
:type seqs: List[List[int]]
:rtype: bool
"""
n = len(org)
graph = collections.defaultdict(set)
visited = {}
incomings = collections.defaultdict(int)
nodes = set()
for seq in seqs:
if len(seq) == 1:
nodes |= {seq[0]}
for i in range(0, len(seq) - 1):
start, end = seq[i], seq[i+1]
nodes |= {start, end}

order = []
visited = collections.defaultdict(int)
def dfs(root, graph, order, visited, incomings):
visited[root] = 1
nbrs = graph.get(root, [])
for nbr in graph.get(root, []):
visit = visited.get(nbr, 0)
if visit == 0:
incomings[nbr] += 1
if not dfs(nbr, graph, order, visited, incomings):
return False
elif visit == 1:
return False
elif visit == 2:
incomings[nbr] += 1
order.append(root)
visited[root] = 2
return True

for node in nodes:
if visited[node] == 0:
if not dfs(node, graph, order, visited, incomings):
return False
count = 0
for node in incomings:
if incomings[node] == 0:
count += 1
if count == 2:
return False
if order[::-1] == org:
return True
return False
``````

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