結果

問題 No.1333 Squared Sum
ユーザー maspy
提出日時 2021-01-08 21:45:44
言語 PyPy3
(7.3.15)
結果
AC  
実行時間 910 ms / 2,000 ms
コード長 1,499 bytes
コンパイル時間 462 ms
コンパイル使用メモリ 82,304 KB
実行使用メモリ 153,492 KB
最終ジャッジ日時 2024-11-16 12:06:29
合計ジャッジ時間 24,716 ms
ジャッジサーバーID
(参考情報)
judge5 / judge4
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ファイルパターン 結果
other AC * 44
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ソースコード

diff #
プレゼンテーションモードにする

import sys
read = sys.stdin.buffer.read
readline = sys.stdin.buffer.readline
readlines = sys.stdin.buffer.readlines
MOD = 1_000_000_007
def bfs_tree(N, G, root=1):
q = [root]
parent = [0] * (N + 1)
dist = [0] * (N + 1)
for v in q:
for w, cost in G[v]:
if w == parent[v]:
continue
dist[w] = dist[v] + cost
parent[w] = v
q.append(w)
return parent, q, dist
def main(N, G):
parent, order, dist = bfs_tree(N, G)
ans = 0
# k
dp_0 = [0] * (N + 1)
dp_1 = [0] * (N + 1)
dp_2 = [0] * (N + 1)
dp = [0] * (N + 1) # lca
for v in order[::-1]:
dp_0[v] += 1
dp[v] += dp_2[v] * dp_0[v] * 2
dp[v] += 2 * dp_1[v]**2
dp_0[v] %= MOD
dp_1[v] %= MOD
dp_2[v] %= MOD
dp[v] %= MOD
p = parent[v]
if p == 0:
break
d = dist[v] - dist[p]
dp[p] -= dp_0[v] * dp_2[v] * 2 + 4 * d * d * dp_0[v]**2
dp[p] -= 2 * dp_1[v] * dp_1[v]
dp[p] -= 8 * d * dp_0[v] * dp_1[v]
dp_0[p] += dp_0[v]
dp_1[p] += dp_1[v] + d * dp_0[v]
dp_2[p] += dp_2[v] + 2 * d * dp_1[v] + d * d * dp_0[v]
ans = sum(dp) % MOD
if ans & 1:
ans += MOD
ans //= 2
return ans
N = int(readline())
G = [[] for _ in range(N + 1)]
for line in readlines():
a, b, c = map(int, line.split())
G[a].append((b, c))
G[b].append((a, c))
print(main(N, G))
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