#1007247 (Rust) No.797 Noelちゃんとピラミッド

• 問題: No.797 Noelちゃんとピラミッド
• ユーザー: Yukino DX.
• 提出日時: 2024-09-06 10:15:39
• 言語: Rust (1.83.0 + proconio)
• 結果: AC
• 実行時間: 10 ms / 2,000 ms
• コード長: 4,300 bytes
• コンパイル時間: 11,525 ms
• コンパイル使用メモリ: 404,292 KB
• 実行使用メモリ: 6,944 KB
• 最終ジャッジ日時: 2024-09-06 10:15:57
• 合計ジャッジ時間: 14,787 ms
• ジャッジサーバーID （参考情報）: judge4 / judge1

ファイルパターン	結果
sample	AC * 3
other	AC * 60

ソースコード

use proconio::input;

fn main() {
    input! {
        n:usize,
        a:[usize;n],
    }

    let comb = Combination::<MOD>::new(n - 1);
    let mut ans = ModInt::<MOD>::new(0);
    for i in 0..n {
        ans += ModInt::new(a[i]) * comb.comb(n - 1, i);
    }

    println!("{}", ans);
}

const MOD: usize = 1000000007;
use combination::*;
use modint::*;
mod combination {
    use crate::modint::*;

    pub struct Combination<const MOD: usize> {
        fac: Vec<ModInt<MOD>>,
        finv: Vec<ModInt<MOD>>,
    }

    impl<const MOD: usize> Combination<MOD> {
        pub fn new(n: usize) -> Self {
            let mut fac = vec![ModInt::new(1); n + 1];
            let mut inv = vec![ModInt::new(1); n + 1];
            let mut finv = vec![ModInt::new(1); n + 1];

            for i in 2..=n {
                fac[i] = fac[i - 1] * ModInt::<MOD>::new(i);
                inv[i] = -inv[MOD % i] * ModInt::<MOD>::new(MOD / i);
                finv[i] = finv[i - 1] * inv[i];
            }

            Self { fac, finv }
        }

        pub fn comb(&self, n: usize, k: usize) -> ModInt<MOD> {
            if n < k {
                ModInt::new(0)
            } else {
                self.fac[n] * self.finv[n - k] * self.finv[k]
            }
        }
    }
}

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
        }
    }
}