結果

問題 No.1333 Squared Sum
ユーザー toyuzuko
提出日時 2021-04-18 00:17:35
言語 PyPy3
(7.3.15)
結果
AC  
実行時間 1,192 ms / 2,000 ms
コード長 2,431 bytes
コンパイル時間 142 ms
コンパイル使用メモリ 82,304 KB
実行使用メモリ 204,816 KB
最終ジャッジ日時 2024-07-04 04:22:11
合計ジャッジ時間 29,963 ms
ジャッジサーバーID
(参考情報)
judge3 / judge2
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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

class Tree():
def __init__(self, n):
self.n = n
self.tree = [[] for _ in range(n)]
self.root = None
def add_edge(self, u, v, c):
if u > v: u, v = v, u
self.tree[u].append((v, c))
self.tree[v].append((u, c))
def set_root(self, r=0):
self.root = r
self.par = [None] * self.n
self.ord = [r]
self.cost = [0] * N
stack = [r]
while stack:
v = stack.pop()
for adj, cost in self.tree[v]:
if self.par[v] == adj: continue
self.cost[adj] = cost
self.par[adj] = v
self.ord.append(adj)
stack.append(adj)
def rerooting(self, op, e, merge, id):
if self.root is None: self.set_root()
dp = [e] * self.n
lt = [id] * self.n
rt = [id] * self.n
inv = [id] * self.n
for v in self.ord[::-1]:
tl = tr = e
for adj, cost in self.tree[v]:
if self.par[v] == adj: continue
lt[adj] = tl
tl = op(tl, dp[adj], cost)
for adj, cost in self.tree[v][::-1]:
if self.par[v] == adj: continue
rt[adj] = tr
tr = op(tr, dp[adj], cost)
dp[v] = tr
for v in self.ord:
if v == self.root: continue
p = self.par[v]
inv[v] = op(merge(lt[v], rt[v]), inv[p], self.cost[p])
dp[v] = op(dp[v], inv[v], self.cost[v])
return dp
import io, os
input = io.BytesIO(os.read(0, os.fstat(0).st_size)).readline
MOD = 1000000007
N = int(input())
t = Tree(N)
for _ in range(N - 1):
u, v, w = map(int, input().split())
u -= 1; v -= 1
t.add_edge(u, v, w)
def op(p, v, d):
p_size, p_dist, p_square = p
v_size, v_dist, v_square = v
size = p_size + v_size
dist = (p_dist + v_dist + d * v_size) % MOD
square = (p_square + v_square + d**2 * v_size + 2 * d * v_dist) % MOD
return size, dist, square
def merge(lt, rt):
l_size, l_dist, l_square = lt
r_size, r_dist, r_square = rt
size = l_size + r_size - 1
dist = (l_dist + r_dist) % MOD
square = (l_square + r_square) % MOD
return size, dist, square
dp = t.rerooting(op, (1, 0, 0), merge, (0, 0, 0))
res = 0
for size, dist, square in dp:
res += square
res %= MOD
print(res * pow(2, MOD - 2, MOD) % MOD)
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