結果

問題 No.1333 Squared Sum
ユーザー chineristAC
提出日時 2021-01-08 21:44:37
言語 PyPy3
(7.3.15)
結果
AC  
実行時間 1,041 ms / 2,000 ms
コード長 1,565 bytes
コンパイル時間 286 ms
コンパイル使用メモリ 82,432 KB
実行使用メモリ 144,956 KB
最終ジャッジ日時 2024-11-16 11:01:10
合計ジャッジ時間 28,664 ms
ジャッジサーバーID
（参考情報） 		judge3 / judge1
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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
from collections import deque
mod = 10**9+7
input = sys.stdin.readline
N = int(input())
edge = [[] for i in range(N)]
for i in range(N-1):
    u,v,w = map(int,input().split())
    edge[u-1].append((v-1,w))
    edge[v-1].append((u-1,w))
deq = deque([0])
parent = [-1]*N
parent[0] = (0,0)
res = []
while deq:
    v = deq.popleft()
    res.append(v)
    for nv,w in edge[v]:
        if parent[nv]==-1:
            parent[nv] = (v,w)
            deq.append(nv)
res = res[::-1]
size = [1 for v in range(N)]
dist_sum = [0 for v in range(N)]
dist_sum_square = [0 for v in range(N)]
for v in res:
    for nv,w in edge[v]:
        if nv!=parent[v][0]:
            size[v] += size[nv]
            dist_sum[v] += dist_sum[nv] + w * size[nv]
            dist_sum[v] %= mod
            dist_sum_square[v] += dist_sum_square[nv] + 2 * w * dist_sum[nv] + size[nv] * w * w
            dist_sum_square[v] %= mod
#4 9 1 3
ans = [0 for v in range(N)]
ans[0] = dist_sum_square[0]
dist_sum_ans = [0 for v in range(N)]
dist_sum_ans[0] = dist_sum[0]
res = res[::-1]
for v in res:
    if v==0:
        continue
    pv,w = parent[v]
    tmp = ans[pv] - ( dist_sum_square[v] + 2 * w * dist_sum[v] + size[v] * w * w )
    tmp_dist_sum = dist_sum_ans[pv] - (w * size[v] + dist_sum[v])
    ans[v] = dist_sum_square[v] + tmp + 2 * w * (tmp_dist_sum) + (N - size[v]) * w * w
    dist_sum_ans[v] = dist_sum[v] + w * (N - size[v]) + tmp_dist_sum
    ans[v] %= mod
    dist_sum_ans[v] %= mod
S = 0
for v in range(N):
    S += ans[v]
    S %= mod
S *= pow(2,mod-2,mod)
print(S%mod)
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