結果

問題 No.827 総神童数
ユーザー Yukino DX.
提出日時 2024-09-08 21:46:32
言語 Rust
(1.83.0 + proconio)
結果
AC  
実行時間 120 ms / 2,000 ms
コード長 4,045 bytes
コンパイル時間 14,814 ms
コンパイル使用メモリ 388,268 KB
実行使用メモリ 40,096 KB
最終ジャッジ日時 2024-09-08 21:46:52
合計ジャッジ時間 18,989 ms
ジャッジサーバーID
(参考情報)
judge3 / judge5
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 * 36
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

use proconio::{input, marker::Usize1};
fn main() {
input! {
n:usize,
uv:[(Usize1,Usize1);n-1],
}
let mut g = vec![vec![]; n];
for &(u, v) in uv.iter() {
g[u].push(v);
g[v].push(u);
}
let mut cnts = vec![0; n];
dfs(0, n, &g, &mut cnts, 0);
let mut facs = vec![ModInt::<MOD>::new(1); n + 1];
for i in 0..n {
facs[i + 1] = facs[i] * ModInt::new(i + 1);
}
let mut f = vec![ModInt::new(0); n];
for i in 0..n {
f[i] = facs[n - i - 1] * ModInt::new(n - i) * facs[n] / (ModInt::new(i + 1) * facs[n - i]);
}
let mut ans = ModInt::new(0);
for i in 0..n {
ans += f[cnts[i]];
}
println!("{}", ans);
}
fn dfs(crr: usize, prv: usize, g: &Vec<Vec<usize>>, cnts: &mut Vec<usize>, cnt: usize) {
cnts[crr] = cnt;
for &nxt in g[crr].iter() {
if nxt == prv {
continue;
}
dfs(nxt, crr, g, cnts, cnt + 1);
}
}
const MOD: usize = 1000000007;
use modint::*;
mod modint {
use std::fmt;
use std::ops;
#[derive(Copy, Clone, PartialEq, Eq)]
pub struct ModInt<const MOD: usize> {
pub val: usize,
}
impl<const MOD: usize> ModInt<MOD> {
pub fn new(val: usize) -> Self {
Self { val: val % MOD }
}
pub fn pow(mut self, mut e: usize) -> Self {
let mut res = Self::new(1);
while 0 < e {
if e & 1 != 0 {
res *= self;
}
self *= self;
e >>= 1;
}
res
}
}
impl<const MOD: usize> From<usize> for ModInt<MOD> {
fn from(value: usize) -> Self {
Self { val: value % MOD }
}
}
impl<const MOD: usize> fmt::Display for ModInt<MOD> {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
write!(f, "{}", self.val)
}
}
impl<const MOD: usize> fmt::Debug for ModInt<MOD> {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
write!(f, "{}", self.val)
}
}
impl<const MOD: usize> ops::Neg for ModInt<MOD> {
type Output = Self;
fn neg(self) -> Self::Output {
Self {
val: (MOD - self.val) % MOD,
}
}
}
impl<const MOD: usize> ops::Add for ModInt<MOD> {
type Output = Self;
fn add(self, rhs: Self) -> Self::Output {
Self {
val: (self.val + rhs.val) % MOD,
}
}
}
impl<const MOD: usize> ops::AddAssign for ModInt<MOD> {
fn add_assign(&mut self, rhs: Self) {
*self = *self + rhs;
}
}
impl<const MOD: usize> ops::Mul for ModInt<MOD> {
type Output = Self;
fn mul(self, rhs: Self) -> Self::Output {
Self {
val: self.val * rhs.val % MOD,
}
}
}
impl<const MOD: usize> ops::MulAssign for ModInt<MOD> {
fn mul_assign(&mut self, rhs: Self) {
*self = *self * rhs;
}
}
impl<const MOD: usize> ops::Sub for ModInt<MOD> {
type Output = Self;
fn sub(mut self, rhs: Self) -> Self::Output {
if self.val < rhs.val {
self.val += MOD;
}
Self {
val: (self.val - rhs.val) % MOD,
}
}
}
impl<const MOD: usize> ops::SubAssign for ModInt<MOD> {
fn sub_assign(&mut self, rhs: Self) {
if self.val < rhs.val {
self.val += MOD;
}
*self = *self - rhs;
}
}
impl<const MOD: usize> ops::Div for ModInt<MOD> {
type Output = Self;
fn div(self, rhs: Self) -> Self {
assert!(rhs.val != 0);
self * rhs.pow(MOD - 2)
}
}
impl<const MOD: usize> ops::DivAssign for ModInt<MOD> {
fn div_assign(&mut self, rhs: Self) {
*self = *self / rhs
}
}
}
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