結果

問題 No.1813 Magical Stones
ユーザー MasKoaTSMasKoaTS
提出日時 2024-11-30 21:58:43
言語 PyPy3
(7.3.15)
結果
AC  
実行時間 493 ms / 2,000 ms
コード長 2,554 bytes
コンパイル時間 568 ms
コンパイル使用メモリ 82,304 KB
実行使用メモリ 139,792 KB
最終ジャッジ日時 2024-11-30 21:58:58
合計ジャッジ時間 11,995 ms
ジャッジサーバーID
(参考情報)
judge2 / judge5
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 * 40
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

import sys
input = sys.stdin.readline
"""
SCC
ref : https://manabitimes.jp/math/1250
"""
class SCC:
def __init__(self, n):
self.n = n
self.route = [[] for _ in [0] * n]
self.rev_route = [[] for _ in [0] * n]
self.label = [-1] * n
self.count = 0
def add_edge(self, v_first, v_second):
self.route[v_first].append(v_second)
self.rev_route[v_second].append(v_first)
def _build(self):
self.v_list = []
self.visited = set([])
for v in range(self.n):
if(v in self.visited):
continue
self._dfs(v)
for v in reversed(self.v_list):
if(self.label[v] != -1):
continue
self._rev_dfs(v)
self.count += 1
def _dfs(self, v_start):
stack = [v_start, 0]
while(stack):
v, id = stack[-2:]
if(id == 0 and v in self.visited):
stack.pop()
stack.pop()
continue
self.visited.add(v)
if(id < len(self.route[v])):
stack[-1] += 1
stack.extend([self.route[v][id], 0])
continue
stack.pop()
self.v_list.append(stack.pop())
def _rev_dfs(self, v_start):
stack = [v_start]
self.label[v_start] = self.count
while(stack):
v_now = stack.pop()
for v_next in self.rev_route[v_now]:
if(self.label[v_next] != -1):
continue
self.label[v_next] = self.count
stack.append(v_next)
def construct(self):
self._build()
dag = [[] for _ in [0] * self.count]
group = [[] for _ in [0] * self.count]
for v, lb in enumerate(self.label):
for v_next in self.route[v]:
lb_next = self.label[v_next]
if(lb == lb_next):
continue
dag[lb].append(lb_next)
group[lb].append(v)
return dag, group
'''
Main Code
'''
n, m = map(int, input().split())
edges = [[x - 1 for x in map(int, input().split())] for _ in [0] * m]
scc = SCC(n)
for x, y in edges:
scc.add_edge(x, y)
dag, _ = scc.construct()
N = len(dag)
if(N == 1):
exit(print(0))
zero_in = [True] * N
zero_out = [True] * N
for i in range(N):
if(dag[i]):
zero_out[i] = False
for j in dag[i]:
zero_in[j] = False
ans = max(sum(zero_in), sum(zero_out))
print(ans)
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