結果

問題 No.1976 Cut then Connect
ユーザー tktk_snsntktk_snsn
提出日時 2022-06-10 23:17:36
言語 PyPy3
(7.3.15)
結果
WA  
実行時間 -
コード長 1,728 bytes
コンパイル時間 300 ms
コンパイル使用メモリ 82,436 KB
実行使用メモリ 91,624 KB
最終ジャッジ日時 2024-09-21 06:50:47
合計ジャッジ時間 4,926 ms
ジャッジサーバーID
(参考情報)
judge2 / judge4
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 * 2
other AC * 5 WA * 26
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.buffer.readline
sys.setrecursionlimit(10 ** 7)
inf = 10 ** 9
def dfs(N, root, G):
que = [root]
dist = [-1] * N
par = [-1] * N
dist[root] = 0
while que:
s = que.pop()
for t in G[s]:
if t == par[s]:
continue
par[t] = s
dist[t] = dist[s] + 1
que.append(t)
return dist, par
def search(N, path, G):
M = len(path)
res = [0] * M
d = [-1] * N
for i in range(M):
ng = set()
if i:
ng.add(path[i-1])
if i < M - 1:
ng.add(path[i+1])
que = [path[i]]
d[path[i]] = 0
while que:
s = que.pop()
for t in G[s]:
if t in ng:
continue
if d[t] == -1:
d[t] = d[s] + 1
que.append(t)
res[i] = max(res[i], d[t])
return res
def calc(path, branch):
M = len(path)
res = []
d = 0
for i in range(M):
d = max(d, i + branch[i])
res.append((d + 1) // 2)
return res
N = int(input())
G = [[] for _ in range(N)]
for _ in range(N-1):
a, b = map(int, input().split())
a -= 1
b -= 1
G[a].append(b)
G[b].append(a)
r0 = 0
d0, p0 = dfs(N, r0, G)
r1 = d0.index(max(d0))
d1, p1 = dfs(N, r1, G)
r2 = d1.index(max(d1))
path = [r2]
while 1:
x = p1[path[-1]]
if x == -1:
break
path.append(x)
M = len(path)
dep = [min(i, M - i - 1) for i in range(M)]
branch = search(N, path, G)
L = calc(path, branch)
R = calc(path[::-1], branch[::-1])[::-1]
ans = M - 1
for i in range(M - 1):
ans = min(ans, L[i] + R[i+1] + 1)
print(ans)
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