結果

問題 No.1507 Road Blocked
ユーザー 👑 obakyan
提出日時 2021-05-16 20:05:35
言語 Lua
(LuaJit 2.1.1734355927)
結果
AC  
実行時間 238 ms / 2,000 ms
コード長 1,945 bytes
コンパイル時間 83 ms
コンパイル使用メモリ 6,948 KB
実行使用メモリ 21,760 KB
最終ジャッジ日時 2024-10-05 05:55:31
合計ジャッジ時間 8,838 ms
ジャッジサーバーID
(参考情報)
judge3 / judge2
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 * 30
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

local mod = 998244353
local mfl = math.floor
local function bmul(x, y)
local x0, y0 = x % 31596, y % 31596
local x1, y1 = mfl(x / 31596), mfl(y / 31596)
return (x1 * y1 * 62863 + (x1 * y0 + x0 * y1) * 31596 + x0 * y0) % mod
end
local function badd(x, y)
return (x + y) % mod
end
local function bsub(x, y)
return (x + mod - y) % mod
end
local function modpow(src, pow)
local res = 1
while 0 < pow do
if pow % 2 == 1 then
res = bmul(res, src)
pow = pow - 1
end
src = bmul(src, src)
pow = mfl(pow / 2)
end
return res
end
local function modinv(src)
return modpow(src, mod - 2)
end
local n = io.read("*n")
local edge = {}
local parent = {}
local childask = {}
local childcnt = {}
for i = 1, n do
edge[i] = {}
parent[i] = 0
childask[i] = 0
childcnt[i] = 0
end
local ea, eb, ec = {}, {}, {}
for i = 1, n - 1 do
local a, b = io.read("*n", "*n")
ea[i] = a
eb[i] = b
table.insert(edge[a], b)
table.insert(edge[b], a)
end
local tasks = {1}
for i = 1, n do
local src = tasks[i]
for j = 1, #edge[src] do
local dst = edge[src][j]
if parent[src] ~= dst then
parent[dst] = src
table.insert(tasks, dst)
childask[src] = childask[src] + 1
end
end
end
tasks = {}
for i = 2, n do
if childask[i] == 0 then
table.insert(tasks, i)
end
end
local ret = 0
for i = 1, n do
local src = tasks[i]
for j = 1, #edge[src] do
local child = edge[src][j]
if child ~= parent[src] then
local a = childcnt[child] + 1
local b = n - a
local numer = badd(bmul(a, a - 1), bmul(b, b - 1))
local denom = badd(numer, bmul(2 * a, b))
ret = badd(ret, bmul(numer, modinv(denom)))
end
end
local p = parent[src]
if 0 < p then
childask[p] = childask[p] - 1
childcnt[p] = childcnt[p] + 1 + childcnt[src]
if childask[p] == 0 then
table.insert(tasks, p)
end
end
end
ret = bmul(ret, modinv(n - 1))
print(ret)
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0