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优化Bellman-Ford算法中去重加入队列的判断 O(n) -> O(1) #1

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优化Bellman-Ford算法中去重加入队列的判断 O(n) -> O(1) #1

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9 changes: 6 additions & 3 deletions problems/kamacoder/0095.城市间货物运输II.md
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Original file line number Diff line number Diff line change
Expand Up @@ -502,18 +502,21 @@ def main():
min_dist[1] = 0 # 初始化
count[1] = 1
d = deque([1])
in_queue = [False for _ in range(n+1)]
flag = False

while d: # 主循环
cur_node = d.popleft()
in_queue[cur_node] = False
for next_node, val in graph[cur_node]:
if min_dist[next_node] > min_dist[cur_node] + val:
min_dist[next_node] = min_dist[cur_node] + val
if next_node not in d:
if not in_queue[next_node]:
count[next_node] += 1
d.append(next_node)
if count[next_node] == n: # 如果某个点松弛了n次，说明有负回路
flag = True
in_queue[next_node] = True
if count[next_node] == n: # 如果某个点松弛了n次，说明有负回路
flag = True
if flag:
break

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