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Copy path210_Course_Schedule_II.py
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210_Course_Schedule_II.py
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54 lines (45 loc) · 1.88 KB
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from collections import deque
class Solution:
def findOrder(self, numCourses: int, prerequisites: List[List[int]]) -> List[int]:
if numCourses == 0:
return []
degrees = [0 for _ in range(numCourses)]
edges = {i: [] for i in range(numCourses)}
order = []
for i, j in prerequisites:
degrees[i] += 1 # 被指向的node degree + 1
edges[j].append(i) # edge 對應關係 j -> i
start_nodes = [n for n in range(numCourses) if degrees[n] == 0]
queue = deque(start_nodes)
while queue:
head = queue.popleft()
order.append(head)
for neighbor in edges[head]:
degrees[neighbor] -= 1
if degrees[neighbor] == 0:
queue.append(neighbor)
return order if len(order) == numCourses else [] # Note: if no solution return []
# use queue object
import queue
class Solution:
def findOrder(self, numCourses, prerequisites):
if numCourses == 0:
return []
degrees = [0 for _ in range(numCourses)]
edges = {i: [] for i in range(numCourses)}
order = []
for i, j in prerequisites:
degrees[i] += 1 # 被指向的node degree + 1
edges[j].append(i) # edge 對應關係 j -> i
q = queue.Queue(numCourses) # "queue.Queue(maxsize)"
start_nodes = [n for n in range(numCourses) if degrees[n] == 0]
for node in start_nodes:
q.put(node)
while not q.empty(): # use empty() to check
head = q.get()
order.append(head)
for neighbor in edges[head]:
degrees[neighbor] -= 1
if degrees[neighbor] == 0:
q.put(neighbor)
return order if len(order) == numCourses else [] # Note: if no solution return []