結果

問題 No.1976 Cut then Connect
ユーザー tamatotamato
提出日時 2022-06-10 23:09:28
言語 PyPy3
(7.3.15)
結果
RE  
実行時間 -
コード長 3,785 bytes
コンパイル時間 176 ms
コンパイル使用メモリ 82,048 KB
実行使用メモリ 138,668 KB
最終ジャッジ日時 2024-09-21 06:48:46
合計ジャッジ時間 7,689 ms
ジャッジサーバーID
(参考情報)
judge3 / judge1
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 * 1 RE * 1
other AC * 11 WA * 7 RE * 13
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

mod = 998244353
def main():
import sys
from collections import deque
input = sys.stdin.readline
def radius(v0, v1):
que = deque()
que.append(v0)
seen = {}
seen[v0] = 0
v_last = 0
while que:
v = que.popleft()
for u in adj[v]:
if u == v1:
continue
if u not in seen:
seen[u] = seen[v] + 1
que.append(u)
v_last = v
v0 = v_last
que = deque()
que.append(v0)
seen = {}
seen[v0] = 0
v_last = 0
while que:
v = que.popleft()
for u in adj[v]:
if u == v1:
continue
if u not in seen:
seen[u] = seen[v] + 1
que.append(u)
v_last = v
return seen[v_last]
N = int(input())
adj = [[] for _ in range(N + 1)]
for _ in range(N - 1):
a, b = map(int, input().split())
adj[a].append(b)
adj[b].append(a)
que = deque()
que.append(1)
seen = [-1] * (N+1)
seen[1] = 0
par = [0] * (N+1)
child = [[] for _ in range(N+1)]
seq = []
while que:
v = que.popleft()
seq.append(v)
for u in adj[v]:
if seen[u] == -1:
seen[u] = seen[v] + 1
par[u] = v
child[v].append(u)
que.append(u)
seq.reverse()
v0 = seq[0]
que = deque()
que.append(v0)
seen = [-1] * (N+1)
seen[v0] = 0
par = [0] * (N+1)
child = [[] for _ in range(N+1)]
seq = []
while que:
v = que.popleft()
seq.append(v)
for u in adj[v]:
if seen[u] == -1:
seen[u] = seen[v] + 1
par[u] = v
child[v].append(u)
que.append(u)
seq.reverse()
v1 = seq[0]
D = seen[v1]
if D & 1:
v = v1
for _ in range(D // 2):
v = par[v]
vl = v
vr = par[v]
dl = radius(vl, vr)
dr = radius(vr, vl)
print(max((dl + 1) // 2 + (dr + 1) // 2 + 1, dl, dr))
assert False
else:
ans = N * 2
v = v1
for _ in range(D // 2):
v = par[v]
v0 = v
que = deque()
que.append(v0)
seen = [-1] * (N+1)
seen[v0] = 0
par = [0] * (N+1)
child = [[] for _ in range(N+1)]
seq = []
while que:
v = que.popleft()
seq.append(v)
for u in adj[v]:
if seen[u] == -1:
seen[u] = seen[v] + 1
par[u] = v
child[v].append(u)
que.append(u)
seq.reverse()
subtree_len = [(0, 0)]
for c in child[v0]:
que = deque()
seq = []
que.append(c)
while que:
v = que.popleft()
for vv in child[v]:
que.append(vv)
seq.append(v)
subtree_len.append((seen[seq[-1]], c))
subtree_len.sort(key=lambda x: x[0], reverse=True)
for c in child[v0]:
dc = radius(c, v0)
if c == subtree_len[0][1]:
dc2 = subtree_len[1][0] + subtree_len[2][0]
elif c == subtree_len[1][1]:
dc2 = subtree_len[0][0] + subtree_len[2][0]
else:
dc2 = subtree_len[0][0] + subtree_len[1][0]
ans = min(ans, max((dc + 1) // 2 + (dc2 + 1) // 2 + 1, dc, dc2))
#print(cc, ans, dc, dc2)
print(ans)
#print(subtree_len)
if __name__ == '__main__':
main()
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