結果

問題 No.1227 I hate ThREE
ユーザー chineristACchineristAC
提出日時 2020-09-11 22:57:33
言語 PyPy3
(7.3.15)
結果
AC  
実行時間 162 ms / 2,000 ms
コード長 2,846 bytes
コンパイル時間 346 ms
コンパイル使用メモリ 82,080 KB
実行使用メモリ 102,948 KB
最終ジャッジ日時 2025-01-02 05:44:33
合計ジャッジ時間 4,216 ms
ジャッジサーバーID
(参考情報)
judge2 / 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 * 3
other AC * 33
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.readline
sys.setrecursionlimit(2*10**5)
mod = 10**9+7
N,C = map(int,input().split())
edge = [[] for i in range(N)]
for i in range(N-1):
a,b = map(int,input().split())
edge[a-1].append(b-1)
edge[b-1].append(a-1)
depth = [-1 for i in range(N)]
parent = [-1 for i in range(N)]
size = [1 for i in range(N)]
depth[0] = 0
def dfs(v,pv):
for nv in edge[v]:
if nv!=pv:
parent[nv] = v
depth[nv] = depth[v] + 1
dfs(nv,v)
size[v] += size[nv]
dfs(0,-1)
D = max(depth)
def solve(M):
if M<=2*D+1:
dp = [[1 for i in range(M)] for j in range(N)]
def dp_dfs(v,pv):
for nv in edge[v]:
if nv!=pv:
dp_dfs(nv,v)
for i in range(M):
tmp = 0
if i!=0:
tmp += dp[nv][i-1]
if i!=M-1:
tmp += dp[nv][i+1]
tmp %= mod
dp[v][i] *= tmp
dp[v][i] %= mod
dp_dfs(0,-1)
res = 0
for i in range(M):
res += dp[0][i]
res %= mod
return res
else:
dp_low = [[1 for i in range(D+1)] for j in range(N)]
dp_high = [[1 for i in range(D+1)] for j in range(N)]
def dp_dfs(v,pv):
for nv in edge[v]:
if nv!=pv:
dp_dfs(nv,v)
for i in range(D+1):
tmp = 0
if i!=0:
tmp += dp_low[nv][i-1]
if i!=D:
tmp += dp_low[nv][i+1]
else:
tmp += pow(2,size[nv]-1,mod)
tmp %= mod
dp_low[v][i] *= tmp
dp_low[v][i] %= mod
tmp = 0
if i!=0:
tmp += dp_high[nv][i-1]
if i!=D:
tmp += dp_high[nv][i+1]
else:
tmp += pow(2,size[nv]-1,mod)
tmp %= mod
dp_high[v][i] *= tmp
dp_high[v][i] %= mod
dp_dfs(0,-1)
res = 0
for i in range(D+1):
res += dp_low[0][i]
res %= mod
res += dp_high[0][i]
res %= mod
tmp = pow(2,N-1,mod) * (M-2*D-2) %mod
res += tmp
res %= mod
return res
ans = 0
c = C//3
if C%3==1:
ans += solve(c+1) + 2*solve(c)
ans %= mod
elif C%3==2:
ans += 2*solve(c+1) + solve(c)
ans %= mod
else:
ans = 3*solve(c)
ans %= mod
print(ans)
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