結果
問題 | No.2245 Second Smallest |
ユーザー |
![]() |
提出日時 | 2023-03-10 22:28:12 |
言語 | Rust (1.83.0 + proconio) |
結果 |
AC
|
実行時間 | 15 ms / 2,000 ms |
コード長 | 27,473 bytes |
コンパイル時間 | 13,160 ms |
コンパイル使用メモリ | 387,204 KB |
実行使用メモリ | 6,944 KB |
最終ジャッジ日時 | 2024-09-18 04:38:24 |
合計ジャッジ時間 | 14,420 ms |
ジャッジサーバーID (参考情報) |
judge3 / judge4 |
(要ログイン)
ファイルパターン | 結果 |
---|---|
other | AC * 30 |
コンパイルメッセージ
warning: unused import: `std::io::Write` --> src/main.rs:18:5 | 18 | use std::io::Write; | ^^^^^^^^^^^^^^ | = note: `#[warn(unused_imports)]` on by default warning: type alias `Map` is never used --> src/main.rs:21:6 | 21 | type Map<K, V> = BTreeMap<K, V>; | ^^^ | = note: `#[warn(dead_code)]` on by default warning: type alias `Set` is never used --> src/main.rs:22:6 | 22 | type Set<T> = BTreeSet<T>; | ^^^ warning: type alias `Deque` is never used --> src/main.rs:23:6 | 23 | type Deque<T> = VecDeque<T>; | ^^^^^
ソースコード
// k=1 の問題を解けるか// H*W のグリッドを右下で動く時にsecod min の最小値// second min が x以下である確率//// 最小値は解けるか?// これは明らかだった...//// x 未満となるマス目が斜めに連なる確率// second min がx 以上となる確率// sum_{0 <= i <= min(H, W)} C(H, i) C(W, i) x^i (1-x)^(HW-i)// x 以下// 1 - P(x)// 密度// d/dx -P(x)//// ベータ関数とか言うのがあったuse std::io::Write;use std::collections::*;type Map<K, V> = BTreeMap<K, V>;type Set<T> = BTreeSet<T>;type Deque<T> = VecDeque<T>;fn main() {input! {h: usize,w: usize,k: usize,}let pc = precalc::Precalc::new(h + w + k);let mut deq = FoldableDeque::new(|a: &M, b: &M| *a * *b);let mut l = 0;let mut r = 0;// x^m (1-x)^n// m!n!/(m+n+1)! = m! / (m+n+1)(m+n)..(n+1)let mut beta = |m: usize, n: usize| -> M {if l == r {l = n + 1;r = n + 1;}while r < n + m + 2 {deq.push_back(M::from(r));r += 1;}while n + 1 < l {l -= 1;deq.push_front(M::from(l));}while r > n + m + 2 {r -= 1;deq.pop_back();}while n + 1 > l {l += 1;deq.pop_front();}pc.fact(m) * deq.find().unwrap_or(M::one()).inv()};let mut ans = M::zero();for i in 0..=std::cmp::min(h, w) {let mut v = M::zero();v += M::from(i) * beta(k + i - 1, h * w - i);v -= M::from(h * w - i) * beta(k + i, h * w - i - 1);v *= pc.comb(h, i) * pc.comb(w, i);ans -= v;}println!("{}", ans);}// ---------- begin input macro ----------// reference: https://qiita.com/tanakh/items/0ba42c7ca36cd29d0ac8#[macro_export]macro_rules! input {(source = $s:expr, $($r:tt)*) => {let mut iter = $s.split_whitespace();input_inner!{iter, $($r)*}};($($r:tt)*) => {let s = {use std::io::Read;let mut s = String::new();std::io::stdin().read_to_string(&mut s).unwrap();s};let mut iter = s.split_whitespace();input_inner!{iter, $($r)*}};}#[macro_export]macro_rules! input_inner {($iter:expr) => {};($iter:expr, ) => {};($iter:expr, $var:ident : $t:tt $($r:tt)*) => {let $var = read_value!($iter, $t);input_inner!{$iter $($r)*}};}#[macro_export]macro_rules! read_value {($iter:expr, ( $($t:tt),* )) => {( $(read_value!($iter, $t)),* )};($iter:expr, [ $t:tt ; $len:expr ]) => {(0..$len).map(|_| read_value!($iter, $t)).collect::<Vec<_>>()};($iter:expr, chars) => {read_value!($iter, String).chars().collect::<Vec<char>>()};($iter:expr, bytes) => {read_value!($iter, String).bytes().collect::<Vec<u8>>()};($iter:expr, usize1) => {read_value!($iter, usize) - 1};($iter:expr, $t:ty) => {$iter.next().unwrap().parse::<$t>().expect("Parse error")};}// ---------- end input macro ----------// ---------- begin ModInt ----------// モンゴメリ乗算を用いる// ほぼCodeforces用// 注意// new_unchecked は値xが 0 <= x < modulo であることを仮定// ModInt の中身は正規化された値で持ってるので直接読んだり書いたりするとぶっ壊れる// 奇素数のみmod modint {use std::marker::*;use std::ops::*;pub trait Modulo {fn modulo() -> u32;fn rem() -> u32;fn ini() -> u64;fn reduce(x: u64) -> u32 {debug_assert!(x < (Self::modulo() as u64) << 32);let b = (x as u32 * Self::rem()) as u64;let t = x + b * Self::modulo() as u64;let mut c = (t >> 32) as u32;if c >= Self::modulo() {c -= Self::modulo();}c as u32}}#[allow(dead_code)]pub enum Mod1_000_000_007 {}impl Modulo for Mod1_000_000_007 {fn modulo() -> u32 {1_000_000_007}fn rem() -> u32 {2226617417}fn ini() -> u64 {582344008}}#[allow(dead_code)]pub enum Mod998_244_353 {}impl Modulo for Mod998_244_353 {fn modulo() -> u32 {998_244_353}fn rem() -> u32 {998244351}fn ini() -> u64 {932051910}}#[allow(dead_code)]pub fn generate_umekomi_modulo(p: u32) {assert!(p < (1 << 31)&& p > 2&& p & 1 == 1&& (2u32..).take_while(|v| v * v <= p).all(|k| p % k != 0));let mut t = 1u32;let mut s = !p + 1;let mut n = !0u32 >> 2;while n > 0 {if n & 1 == 1 {t *= s;}s *= s;n >>= 1;}let mut ini = (1u64 << 32) % p as u64;ini = (ini << 32) % p as u64;assert!(t * p == !0);println!("pub enum Mod{} {{}}", p);println!("impl Modulo for Mod{} {{", p);println!(" fn modulo() -> u32 {{");println!(" {}", p);println!(" }}");println!(" fn rem() -> u32 {{");println!(" {}", t);println!(" }}");println!(" fn ini() -> u64 {{");println!(" {}", ini);println!(" }}");println!("}}");let mut f = vec![];let mut n = p - 1;for i in 2.. {if i * i > n {break;}if n % i == 0 {f.push(i);while n % i == 0 {n /= i;}}}if n > 1 {f.push(n);}let mut order = 1;let mut n = p - 1;while n % 2 == 0 {n /= 2;order <<= 1;}let z = (2u64..).find(|z| {f.iter().all(|f| mod_pow(*z, ((p - 1) / *f) as u64, p as u64) != 1)}).unwrap();let zeta = mod_pow(z, ((p - 1) / order) as u64, p as u64);println!("impl transform::NTTFriendly for Mod{} {{", p);println!(" fn order() -> usize {{");println!(" {}", order);println!(" }}");println!(" fn zeta() -> u32 {{");println!(" {}", zeta);println!(" }}");println!("}}");}pub struct ModInt<T>(u32, PhantomData<T>);impl<T> Clone for ModInt<T> {fn clone(&self) -> Self {ModInt::build(self.0)}}impl<T> Copy for ModInt<T> {}impl<T: Modulo> Add for ModInt<T> {type Output = ModInt<T>;fn add(self, rhs: Self) -> Self::Output {let mut d = self.0 + rhs.0;if d >= T::modulo() {d -= T::modulo();}Self::build(d)}}impl<T: Modulo> AddAssign for ModInt<T> {fn add_assign(&mut self, rhs: Self) {*self = *self + rhs;}}impl<T: Modulo> Sub for ModInt<T> {type Output = ModInt<T>;fn sub(self, rhs: Self) -> Self::Output {let mut d = self.0 - rhs.0;if self.0 < rhs.0 {d += T::modulo();}Self::build(d)}}impl<T: Modulo> SubAssign for ModInt<T> {fn sub_assign(&mut self, rhs: Self) {*self = *self - rhs;}}impl<T: Modulo> Mul for ModInt<T> {type Output = ModInt<T>;fn mul(self, rhs: Self) -> Self::Output {Self::build(T::reduce(self.0 as u64 * rhs.0 as u64))}}impl<T: Modulo> MulAssign for ModInt<T> {fn mul_assign(&mut self, rhs: Self) {*self = *self * rhs;}}impl<T: Modulo> Neg for ModInt<T> {type Output = ModInt<T>;fn neg(self) -> Self::Output {if self.0 == 0 {Self::zero()} else {Self::build(T::modulo() - self.0)}}}impl<T: Modulo> std::fmt::Display for ModInt<T> {fn fmt<'a>(&self, f: &mut std::fmt::Formatter<'a>) -> std::fmt::Result {write!(f, "{}", self.get())}}impl<T: Modulo> std::fmt::Debug for ModInt<T> {fn fmt<'a>(&self, f: &mut std::fmt::Formatter<'a>) -> std::fmt::Result {write!(f, "{}", self.get())}}impl<T: Modulo> std::str::FromStr for ModInt<T> {type Err = std::num::ParseIntError;fn from_str(s: &str) -> Result<Self, Self::Err> {let val = s.parse::<u32>()?;Ok(ModInt::new(val))}}impl<T: Modulo> From<usize> for ModInt<T> {fn from(val: usize) -> ModInt<T> {ModInt::new_unchecked((val % T::modulo() as usize) as u32)}}impl<T: Modulo> From<u64> for ModInt<T> {fn from(val: u64) -> ModInt<T> {ModInt::new_unchecked((val % T::modulo() as u64) as u32)}}impl<T: Modulo> From<i64> for ModInt<T> {fn from(val: i64) -> ModInt<T> {let m = T::modulo() as i64;ModInt::new((val % m + m) as u32)}}#[allow(dead_code)]impl<T> ModInt<T> {fn build(d: u32) -> Self {ModInt(d, PhantomData)}pub fn zero() -> Self {Self::build(0)}pub fn is_zero(&self) -> bool {self.0 == 0}}#[allow(dead_code)]impl<T: Modulo> ModInt<T> {pub fn new_unchecked(d: u32) -> Self {Self::build(T::reduce(d as u64 * T::ini()))}pub fn new(d: u32) -> Self {Self::new_unchecked(d % T::modulo())}pub fn one() -> Self {Self::new_unchecked(1)}pub fn get(&self) -> u32 {T::reduce(self.0 as u64)}pub fn pow(&self, mut n: u64) -> Self {let mut t = Self::one();let mut s = *self;while n > 0 {if n & 1 == 1 {t *= s;}s *= s;n >>= 1;}t}pub fn inv(&self) -> Self {assert!(!self.is_zero());self.pow((T::modulo() - 2) as u64)}}pub fn mod_pow(mut r: u64, mut n: u64, m: u64) -> u64 {let mut t = 1 % m;while n > 0 {if n & 1 == 1 {t = t * r % m;}r = r * r % m;n >>= 1;}t}}// ---------- end ModInt ----------// ---------- begin Precalc ----------mod precalc {use super::modint::*;#[allow(dead_code)]pub struct Precalc<T> {inv: Vec<ModInt<T>>,fact: Vec<ModInt<T>>,ifact: Vec<ModInt<T>>,}#[allow(dead_code)]impl<T: Modulo> Precalc<T> {pub fn new(n: usize) -> Precalc<T> {let mut inv = vec![ModInt::one(); n + 1];let mut fact = vec![ModInt::one(); n + 1];let mut ifact = vec![ModInt::one(); n + 1];for i in 2..(n + 1) {fact[i] = fact[i - 1] * ModInt::new_unchecked(i as u32);}ifact[n] = fact[n].inv();if n > 0 {inv[n] = ifact[n] * fact[n - 1];}for i in (1..n).rev() {ifact[i] = ifact[i + 1] * ModInt::new_unchecked((i + 1) as u32);inv[i] = ifact[i] * fact[i - 1];}Precalc {inv: inv,fact: fact,ifact: ifact,}}pub fn inv(&self, n: usize) -> ModInt<T> {assert!(n > 0);self.inv[n]}pub fn fact(&self, n: usize) -> ModInt<T> {self.fact[n]}pub fn ifact(&self, n: usize) -> ModInt<T> {self.ifact[n]}pub fn perm(&self, n: usize, k: usize) -> ModInt<T> {if k > n {return ModInt::zero();}self.fact[n] * self.ifact[n - k]}pub fn comb(&self, n: usize, k: usize) -> ModInt<T> {if k > n {return ModInt::zero();}self.fact[n] * self.ifact[k] * self.ifact[n - k]}}}// ---------- end Precalc ----------use modint::*;pub trait NTTFriendly: modint::Modulo {fn order() -> usize;fn zeta() -> u32;}type M = ModInt<Mod998_244_353>;impl NTTFriendly for Mod998_244_353 {fn order() -> usize {8388608}fn zeta() -> u32 {15311432}}// 列に対する命令をテキトーに詰めあわせ// modint, primitive type の2つあたりで使うことを想定// +, -, *// zero を要求してないのに仮定してる場所がある//// 何も考えずに書き始めたらいろいろよくわからないことになった// 整理// 長さが等しいときの加算、減算、dot積はok// 長さが異なるときはどうする?// 0埋めされてるというイメージなので// 加算、減算は素直だがdot積はイマイチ// dot積だけ長さが等しいとしておく?// あるいは0埋めのイメージを消すかuse std::ops::*;pub trait Zero: Sized + Add<Output = Self> {fn zero() -> Self;}pub fn zero<T: Zero>() -> T {T::zero()}impl<T: Modulo> Zero for ModInt<T> {fn zero() -> Self {Self::zero()}}impl Zero for usize {fn zero() -> Self {0}}pub trait ArrayAdd {type Item;fn add(&self, rhs: &[Self::Item]) -> Vec<Self::Item>;}impl<T> ArrayAdd for [T]whereT: Zero + Copy,{type Item = T;fn add(&self, rhs: &[Self::Item]) -> Vec<Self::Item> {let mut c = vec![T::zero(); self.len().max(rhs.len())];c[..self.len()].copy_from_slice(self);c.add_assign(rhs);c}}pub trait ArrayAddAssign {type Item;fn add_assign(&mut self, rhs: &[Self::Item]);}impl<T> ArrayAddAssign for [T]whereT: Add<Output = T> + Copy,{type Item = T;fn add_assign(&mut self, rhs: &[Self::Item]) {assert!(self.len() >= rhs.len());self.iter_mut().zip(rhs).for_each(|(x, a)| *x = *x + *a);}}impl<T> ArrayAddAssign for Vec<T>whereT: Zero + Add<Output = T> + Copy,{type Item = T;fn add_assign(&mut self, rhs: &[Self::Item]) {if self.len() < rhs.len() {self.resize(rhs.len(), T::zero());}self.as_mut_slice().add_assign(rhs);}}pub trait ArraySub {type Item;fn sub(&self, rhs: &[Self::Item]) -> Vec<Self::Item>;}impl<T> ArraySub for [T]whereT: Zero + Sub<Output = T> + Copy,{type Item = T;fn sub(&self, rhs: &[Self::Item]) -> Vec<Self::Item> {let mut c = vec![T::zero(); self.len().max(rhs.len())];c[..self.len()].copy_from_slice(self);c.sub_assign(rhs);c}}pub trait ArraySubAssign {type Item;fn sub_assign(&mut self, rhs: &[Self::Item]);}impl<T> ArraySubAssign for [T]whereT: Sub<Output = T> + Copy,{type Item = T;fn sub_assign(&mut self, rhs: &[Self::Item]) {assert!(self.len() >= rhs.len());self.iter_mut().zip(rhs).for_each(|(x, a)| *x = *x - *a);}}impl<T> ArraySubAssign for Vec<T>whereT: Zero + Sub<Output = T> + Copy,{type Item = T;fn sub_assign(&mut self, rhs: &[Self::Item]) {if self.len() < rhs.len() {self.resize(rhs.len(), T::zero());}self.as_mut_slice().sub_assign(rhs);}}pub trait ArrayDot {type Item;fn dot(&self, rhs: &[Self::Item]) -> Vec<Self::Item>;}impl<T> ArrayDot for [T]whereT: Mul<Output = T> + Copy,{type Item = T;fn dot(&self, rhs: &[Self::Item]) -> Vec<Self::Item> {assert!(self.len() == rhs.len());self.iter().zip(rhs).map(|p| *p.0 * *p.1).collect()}}pub trait ArrayDotAssign {type Item;fn dot_assign(&mut self, rhs: &[Self::Item]);}impl<T> ArrayDotAssign for [T]whereT: MulAssign + Copy,{type Item = T;fn dot_assign(&mut self, rhs: &[Self::Item]) {assert!(self.len() == rhs.len());self.iter_mut().zip(rhs).for_each(|(x, a)| *x *= *a);}}pub trait ArrayMul {type Item;fn mul(&self, rhs: &[Self::Item]) -> Vec<Self::Item>;}impl<T> ArrayMul for [T]whereT: Zero + Mul<Output = T> + Copy,{type Item = T;fn mul(&self, rhs: &[Self::Item]) -> Vec<Self::Item> {if self.is_empty() || rhs.is_empty() {return vec![];}let mut res = vec![zero(); self.len() + rhs.len() - 1];for (i, a) in self.iter().enumerate() {for (c, b) in res[i..].iter_mut().zip(rhs) {*c = *c + *a * *b;}}res}}pub trait ArrayNTT {type Item;fn ntt(&mut self);fn intt(&mut self);fn multiply(&self, rhs: &[Self::Item]) -> Vec<Self::Item>;}impl<T> ArrayNTT for [ModInt<T>]whereT: NTTFriendly,{type Item = ModInt<T>;fn ntt(&mut self) {let f = self;let n = f.len();assert!(n.count_ones() == 1);assert!(n <= T::order());let len = n.trailing_zeros() as usize;let mut es = [ModInt::zero(); 30];let mut ies = [ModInt::zero(); 30];let mut sum_e = [ModInt::zero(); 30];let cnt2 = T::order().trailing_zeros() as usize;let mut e = ModInt::new_unchecked(T::zeta());let mut ie = e.inv();for i in (2..=cnt2).rev() {es[i - 2] = e;ies[i - 2] = ie;e = e * e;ie = ie * ie;}let mut now = ModInt::one();for i in 0..(cnt2 - 1) {sum_e[i] = es[i] * now;now *= ies[i];}for ph in 1..=len {let p = 1 << (len - ph);let mut now = ModInt::one();for (i, f) in f.chunks_exact_mut(2 * p).enumerate() {let (x, y) = f.split_at_mut(p);for (x, y) in x.iter_mut().zip(y.iter_mut()) {let l = *x;let r = *y * now;*x = l + r;*y = l - r;}now *= sum_e[(!i).trailing_zeros() as usize];}}}fn intt(&mut self) {let f = self;let n = f.len();assert!(n.count_ones() == 1);assert!(n <= T::order());let len = n.trailing_zeros() as usize;let mut es = [ModInt::zero(); 30];let mut ies = [ModInt::zero(); 30];let mut sum_ie = [ModInt::zero(); 30];let cnt2 = T::order().trailing_zeros() as usize;let mut e = ModInt::new_unchecked(T::zeta());let mut ie = e.inv();for i in (2..=cnt2).rev() {es[i - 2] = e;ies[i - 2] = ie;e = e * e;ie = ie * ie;}let mut now = ModInt::one();for i in 0..(cnt2 - 1) {sum_ie[i] = ies[i] * now;now *= es[i];}for ph in (1..=len).rev() {let p = 1 << (len - ph);let mut inow = ModInt::one();for (i, f) in f.chunks_exact_mut(2 * p).enumerate() {let (x, y) = f.split_at_mut(p);for (x, y) in x.iter_mut().zip(y.iter_mut()) {let l = *x;let r = *y;*x = l + r;*y = (l - r) * inow;}inow *= sum_ie[(!i).trailing_zeros() as usize];}}let ik = ModInt::new_unchecked((T::modulo() + 1) >> 1).pow(len as u64);for f in f.iter_mut() {*f *= ik;}}fn multiply(&self, rhs: &[Self::Item]) -> Vec<Self::Item> {if self.len().min(rhs.len()) <= 32 {return self.mul(rhs);}let size = (self.len() + rhs.len() - 1).next_power_of_two();let mut f = vec![ModInt::zero(); size];let mut g = vec![ModInt::zero(); size];f[..self.len()].copy_from_slice(self);g[..rhs.len()].copy_from_slice(rhs);f.ntt();g.ntt();f.dot_assign(&g);f.intt();f.truncate(self.len() + rhs.len() - 1);f}}pub trait PolynomialOperation {type Item;fn eval(&self, x: Self::Item) -> Self::Item;fn derivative(&self) -> Vec<Self::Item>;fn integral(&self) -> Vec<Self::Item>;}impl<T: Modulo> PolynomialOperation for [ModInt<T>] {type Item = ModInt<T>;fn eval(&self, x: Self::Item) -> Self::Item {self.iter().rev().fold(ModInt::zero(), |s, a| s * x + *a)}fn derivative(&self) -> Vec<Self::Item> {if self.len() <= 1 {return vec![];}self[1..].iter().enumerate().map(|(k, a)| ModInt::new_unchecked(k as u32 + 1) * *a).collect()}fn integral(&self) -> Vec<Self::Item> {if self.is_empty() {return vec![];}let mut inv = vec![ModInt::one(); self.len() + 1];let mut mul = ModInt::zero();for i in 1..=self.len() {mul += ModInt::one();inv[i] = inv[i - 1] * mul;}let mut prod = inv[self.len()].inv();for i in (1..=self.len()).rev() {inv[i] = self[i - 1] * inv[i - 1] * prod;prod *= mul;mul -= ModInt::one();}inv[0] = ModInt::zero();inv}}pub trait FPSOperation {type Item;fn inverse(&self, n: usize) -> Vec<Self::Item>;fn log(&self, n: usize) -> Vec<Self::Item>;fn exp(&self, n: usize) -> Vec<Self::Item>;}impl<T: NTTFriendly> FPSOperation for [ModInt<T>] {type Item = ModInt<T>;fn inverse(&self, n: usize) -> Vec<Self::Item> {assert!(self.len() > 0 && !self[0].is_zero());let len = n.next_power_of_two();assert!(2 * len <= T::order());let mut b = vec![ModInt::zero(); n];b[0] = self[0].inv();let mut f = Vec::with_capacity(2 * len);let mut g = Vec::with_capacity(2 * len);let mut size = 1;while size < n {g.clear();g.extend(b.iter().take(size));g.resize(2 * size, ModInt::zero());f.clear();f.extend(self.iter().take(2 * size));f.resize(2 * size, ModInt::zero());f.ntt();g.ntt();f.dot_assign(&g);f.intt();f[..size].iter_mut().for_each(|f| *f = ModInt::zero());f.ntt();f.dot_assign(&g);f.intt();for (b, g) in b[size..].iter_mut().zip(&f[size..]) {*b = *b - *g;}size *= 2;}b}fn log(&self, n: usize) -> Vec<Self::Item> {assert!(self.get(0).map_or(false, |p| p.get() == 1));let mut b = self.derivative().multiply(&self.inverse(n));b.truncate(n - 1);let mut b = b.integral();b.resize(n, ModInt::zero());b}fn exp(&self, n: usize) -> Vec<Self::Item> {assert!(self.get(0).map_or(true, |a| a.is_zero()));assert!(n <= T::order());let mut b = vec![ModInt::one()];let mut size = 1;while size < n {size <<= 1;let f = b.log(size);let g = self[..self.len().min(size)].sub(&f);b = b.multiply(&g).add(&b);b.truncate(size);}b.truncate(n);b.resize(n, ModInt::zero());b}}// test// yuki907: https://yukicoder.me/submissions/712523// hhkb2020: https://atcoder.jp/contests/hhkb2020/submissions/26997806//// ---------- begin Foldable Deque ----------pub struct FoldableDeque<T, F> {front: Vec<(T, T)>,back: Vec<(T, T)>,op: F,}impl<T, F> FoldableDeque<T, F>whereT: Clone,F: Fn(&T, &T) -> T,{pub fn new(op: F) -> Self {FoldableDeque {front: Vec::new(),back: Vec::new(),op: op,}}pub fn find(&self) -> Option<T> {match (self.front.last(), self.back.last()) {(Some(a), Some(b)) => Some((self.op)(&a.1, &b.1)),(x, y) => x.or(y).map(|p| p.1.clone()),}}pub fn clear(&mut self) {self.front.clear();self.back.clear();}pub fn len(&self) -> usize {self.front.len() + self.back.len()}pub fn push_back(&mut self, val: T) {let sum = match self.back.last() {Some(p) => (self.op)(&p.1, &val),None => val.clone(),};self.back.push((val, sum));}pub fn push_front(&mut self, val: T) {let sum = match self.front.last() {Some(p) => (self.op)(&val, &p.1),None => val.clone(),};self.front.push((val, sum));}pub fn pop_front(&mut self) -> Option<T> {if self.front.is_empty() {let mut back = std::mem::take(&mut self.back);let m = (back.len() + 1) / 2;for (v, _) in back.drain(..m).rev() {self.push_front(v);}if !back.is_empty() {back[0].1 = back[0].0.clone();let (f, t) = back.split_at_mut(1);let mut pre = &f[0].1;for b in t.iter_mut() {b.1 = (self.op)(pre, &b.0);pre = &b.1;}}self.back = back;}self.front.pop().map(|p| p.0)}pub fn pop_back(&mut self) -> Option<T> {if self.back.is_empty() {let mut front = std::mem::take(&mut self.front);let m = (front.len() + 1) / 2;for (v, _) in front.drain(..m).rev() {self.push_back(v);}if !front.is_empty() {front[0].1 = front[0].0.clone();let (t, f) = front.split_at_mut(1);let mut pre = &t[0].1;for f in f.iter_mut() {f.1 = (self.op)(&f.0, pre);pre = &f.1;}}self.front = front;}self.back.pop().map(|p| p.0)}pub fn front(&self) -> Option<&T> {self.front.last().or_else(|| self.back.get(0)).map(|p| &p.0)}pub fn back(&self) -> Option<&T> {self.back.last().or_else(|| self.front.get(0)).map(|p| &p.0)}pub fn get(&self, k: usize) -> Option<&T> {let f = self.front.len();self.front.get(f - 1 - k).or_else(|| self.back.get(k - f)).map(|p| &p.0)}}// ---------- end Foldable Deque ----------