#586392 (Rust) No.1300 Sum of Inversions

• 問題: No.1300 Sum of Inversions
• ユーザー: Strorkis
• 提出日時: 2020-11-28 15:24:24
• 言語: Rust (1.83.0 + proconio)
• 結果: AC
• 実行時間: 107 ms / 2,000 ms
• コード長: 4,694 bytes
• コンパイル時間: 14,476 ms
• コンパイル使用メモリ: 397,872 KB
• 実行使用メモリ: 19,464 KB
• 最終ジャッジ日時: 2024-09-12 23:01:16
• 合計ジャッジ時間: 16,650 ms
• ジャッジサーバーID （参考情報）: judge5 / judge4

ファイルパターン	結果
sample	AC * 3
other	AC * 34

ソースコード

use std::io::prelude::*;

fn input<R: BufRead>(stdin: &mut R) -> String {
    let mut input = String::new();
    stdin.read_line(&mut input).ok();
    input
}

macro_rules! read {
    ($stdin:expr, [$t:tt; $n:expr]) => {
        (0..$n).map(|_| read!($stdin, $t)).collect::<Vec<_>>()
    };
    ($stdin:expr, [$t:tt]) => {
        input($stdin).split_whitespace().map(|s| parse!(s, $t)).collect::<Vec<_>>()    
    };
    ($stdin:expr, ($($t:tt),*)) => {{
        let input = input($stdin);
        let mut iter = input.split_whitespace();    
        ($(parse!(iter.next().unwrap(), $t)),*)    
    }};
    ($stdin:expr, $t:tt) => {
        parse!(input($stdin).trim(), $t)
    };
}

macro_rules! parse {
    ($s:expr, Chars) => ($s.chars().collect::<Vec<_>>());
    ($s:expr, Usize1) => (parse!($s, usize) - 1);
    ($s:expr, $t:ty) => ($s.parse::<$t>().unwrap());
}

#[derive(Clone, Copy, Debug, Eq, PartialEq, Ord, PartialOrd)]
struct ModInt(i64);

impl ModInt {
    const MOD: i64 = 998_244_353;

    fn new(x: i64) -> ModInt {
        Self(x % Self::MOD)
    }
}

impl std::ops::Add for ModInt {
    type Output = Self;

    fn add(self, other: Self) -> Self {
        let x = self.0 + other.0;
        if x < Self::MOD { Self(x) } else { Self(x - Self::MOD) }
    }
}

impl std::ops::AddAssign for ModInt {
    fn add_assign(&mut self, other: Self) {
        *self = *self + other;
    }
}

impl std::ops::Sub for ModInt {
    type Output = Self;

    fn sub(self, other: Self) -> Self {
        if self.0 < other.0 {
            Self(self.0 + Self::MOD - other.0)
        } else {
            Self(self.0 - other.0)
        }
    }
}

impl std::ops::SubAssign for ModInt {
    fn sub_assign(&mut self, other: Self) {
        *self = *self - other;
    }
}

impl std::ops::Mul for ModInt {
    type Output = Self;

    fn mul(self, other: Self) -> Self {
        Self::new(self.0 * other.0)
    }
}

impl std::ops::MulAssign for ModInt {
    fn mul_assign(&mut self, other: Self) {
        *self = *self * other;
    }
}

impl std::fmt::Display for ModInt {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        write!(f, "{}", self.0)
    }
}

impl std::str::FromStr for ModInt {
    type Err = std::num::ParseIntError;

    fn from_str(s: &str) -> Result<Self, Self::Err> {
        let x = s.parse()?;
        Ok(ModInt::new(x))
    }
}

struct FenwickTree<T> {
    n: usize,
    init: T,
    data: Vec<T>,
}

impl<T: Copy + std::ops::AddAssign> FenwickTree<T> {
    fn new(n: usize, init: T) -> FenwickTree<T> {
        FenwickTree { n, init, data: vec![init; n] }
    }

    fn add(&mut self, mut p: usize, x: T) {
        p += 1;
        while p <= self.n {
            self.data[p - 1] += x;
            p += p & (!p + 1);
        }
    }

    fn sum(&self, mut r: usize) -> T {
        let mut res = self.init;
        while r > 0 {
            res += self.data[r - 1];
            r -= r & (!r + 1);
        }
        res
    }
}

fn solve<R: BufRead, W: Write>(stdin: &mut R, writer: &mut W) {
    let n = read!(stdin, usize);
    let a = read!(stdin, [i64]);

    let mut dedup_a = a.clone();
    dedup_a.sort();
    dedup_a.dedup();
    let m = dedup_a.len();
    let compressed_a: Vec<_> = {
        (0..n).map(|i| dedup_a.binary_search(&a[i]).unwrap()).collect()
    };

    let mut left_count = vec![ModInt(0); n];
    let mut right_count = vec![ModInt(0); n];
    let mut left_sum = vec![ModInt(0); n];
    let mut right_sum = vec![ModInt(0); n];

    let mut count_ft = FenwickTree::new(m, ModInt(0));
    let mut sum_ft = FenwickTree::new(m, ModInt(0));
    for i in 0..n {
        let p = m - 1 - compressed_a[i];
        left_count[i] = count_ft.sum(p);
        left_sum[i] = sum_ft.sum(p);
        count_ft.add(p, ModInt(1));
        sum_ft.add(p, ModInt::new(a[i]));
    }

    let mut count_ft = FenwickTree::new(m, ModInt(0));
    let mut sum_ft = FenwickTree::new(m, ModInt(0));
    for i in (0..n).rev() {
        let p = compressed_a[i];
        right_count[i] = count_ft.sum(p);
        right_sum[i] = sum_ft.sum(p);
        count_ft.add(p, ModInt(1));
        sum_ft.add(p, ModInt::new(a[i]));
    }

    let mut ans = ModInt(0);
    for i in 0..n {
        if left_count[i] * right_count[i] == ModInt(0) { continue; }
        ans += left_count[i] * right_sum[i];
        ans += right_count[i] * left_sum[i];
        ans += ModInt::new(a[i]) * left_count[i] * right_count[i];
    }
    writeln!(writer, "{}", ans).ok();
}

fn main() {
    let stdin = std::io::stdin();
    let stdin = &mut stdin.lock();

    let stdout = std::io::stdout();
    let writer = &mut std::io::BufWriter::new(stdout.lock());

    solve(stdin, writer);
}