結果

問題 No.1507 Road Blocked
ユーザー Strorkis
提出日時 2021-05-15 11:36:32
言語 Rust
(1.83.0 + proconio)
結果
AC  
実行時間 39 ms / 2,000 ms
コード長 3,478 bytes
コンパイル時間 12,445 ms
コンパイル使用メモリ 401,544 KB
実行使用メモリ 19,328 KB
最終ジャッジ日時 2024-10-02 18:09:59
合計ジャッジ時間 15,500 ms
ジャッジサーバーID
(参考情報)
judge3 / 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 * 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

pub mod mod_int {
use std::{fmt, ops};
#[derive(Clone, Copy, Debug)]
pub struct ModInt(u64);
impl ModInt {
const MOD: u64 = 998_244_353;
pub fn new(mut x: u64) -> Self {
if x >= Self::MOD {
x %= Self::MOD;
}
Self(x)
}
pub fn zero() -> Self {
Self(0)
}
pub fn one() -> Self {
Self(1)
}
}
impl From<usize> for ModInt {
fn from(x: usize) -> Self {
Self::new(x as u64)
}
}
impl From<i64> for ModInt {
fn from(mut x: i64) -> Self {
let m = Self::MOD as i64;
if x.abs() >= m {
x %= m;
}
if x < 0 {
x += m
}
Self::new(x as u64)
}
}
impl ops::Add for ModInt {
type Output = Self;
fn add(self, other: Self) -> Self {
let mut x = self.0 + other.0;
if x >= Self::MOD {
x -= Self::MOD;
}
Self(x)
}
}
impl ops::AddAssign for ModInt {
fn add_assign(&mut self, other: Self) {
*self = *self + other;
}
}
impl ops::Sub for ModInt {
type Output = Self;
fn sub(mut self, other: Self) -> Self {
if self.0 < other.0 {
self.0 += Self::MOD;
}
Self(self.0 - other.0)
}
}
impl ops::SubAssign for ModInt {
fn sub_assign(&mut self, other: Self) {
*self = *self - other;
}
}
impl ops::Mul for ModInt {
type Output = Self;
fn mul(self, other: Self) -> Self {
Self::new(self.0 * other.0)
}
}
impl ops::MulAssign for ModInt {
fn mul_assign(&mut self, other: Self) {
*self = *self * other;
}
}
impl fmt::Display for ModInt {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
write!(f, "{}", self.0)
}
}
impl ModInt {
pub fn pow(mut self, mut n: u64) -> Self {
let mut res = Self::one();
while n > 0 {
if n & 1 == 1 {
res *= self;
}
self *= self;
n >>= 1;
}
res
}
pub fn inv(self) -> Self {
self.pow(Self::MOD - 2)
}
}
}
use mod_int::ModInt;
fn dfs(
ans: &mut ModInt,
n: usize, g: &[Vec<usize>], p: ModInt,
prev: usize, from: usize
) -> usize {
let mut count = 0;
for &to in &g[from] {
if to == prev { continue; }
let c = dfs(ans, n, g, p, from, to);
*ans = *ans - ModInt::from(c * (n - c)) * p;
count += c;
}
count + 1
}
fn main() {
let ref mut buf = String::new();
std::io::Read::read_to_string(&mut std::io::stdin(), buf).ok();
let mut iter = buf.split_whitespace();
macro_rules! scan {
($t:ty) => (iter.next().unwrap().parse::<$t>().unwrap());
}
let n = scan!(usize);
let mut g = vec![vec![]; n];
for _ in 0..(n - 1) {
let (u, v) = (scan!(usize) - 1, scan!(usize) - 1);
g[u].push(v);
g[v].push(u);
}
let mut ans = ModInt::one();
let k = n * (n - 1) / 2;
let p = ModInt::from((n - 1) * k).inv();
dfs(&mut ans, n, &g, p, !0, 0);
println!("{}", ans);
}
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