結果

問題 No.1865 Make Cycle
ユーザー NaHCO314
提出日時 2022-02-25 19:22:22
言語 PyPy3
(7.3.15)
結果
AC  
実行時間 775 ms / 3,000 ms
コード長 1,049 bytes
コンパイル時間 274 ms
コンパイル使用メモリ 82,048 KB
実行使用メモリ 213,968 KB
最終ジャッジ日時 2024-07-16 09:00:04
合計ジャッジ時間 13,897 ms
ジャッジサーバーID
(参考情報)
judge4 / judge3
このコードへのチャレンジ
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ファイルパターン 結果
sample AC * 4
other AC * 20
権限があれば一括ダウンロードができます

ソースコード

diff #
プレゼンテーションモードにする

from sys import setrecursionlimit
from pypyjit import set_param
setrecursionlimit(10 ** 6)
set_param("max_unroll_recursion=-1")
def DFS(v, g, seen):
seen[v] = 1
for i in g[v]:
if seen[i] == 1 or (seen[i] == 0 and DFS(i, g, seen)):
return True
seen[v] = 2
return False
def main(n, q, edges):
left, right = -1, q + 1
while abs(left - right) > 1:
mid = (right + left) // 2
g = [[] for _ in range(n)]
for a, b in edges[:mid]:
g[a].append(b)
seen = [0] * n
has_cycle = False
for i in range(n):
if seen[i] == 0 and DFS(i, g, seen):
has_cycle = True
if has_cycle:
right = mid
else:
left = mid
ans = right
return ans if ans != q + 1 else -1
if __name__ == '__main__':
n, q = map(int, input().split())
edges = []
for i in range(q):
a, b = map(int, input().split())
edges.append((a - 1, b - 1))
ans = main(n, q, edges)
print(ans)
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