Submission #2404305

---

Source Code Expand

macro_rules! get {
    ($t:ty) => {
        {
            let mut line: String = String::new();
            std::io::stdin().read_line(&mut line).unwrap();
            line.trim().parse::<$t>().unwrap()
        }
    };
    ($($t:ty),*) => {
        {
            let mut line: String = String::new();
            std::io::stdin().read_line(&mut line).unwrap();
            let mut iter = line.split_whitespace();
            (
                $(iter.next().unwrap().parse::<$t>().unwrap(),)*
            )
        }
    };
    ($t:ty; $n:expr) => {
        (0..$n).map(|_|
                    get!($t)
                   ).collect::<Vec<_>>()
    };
    ($($t:ty),*; $n:expr) => {
        (0..$n).map(|_|
                    get!($($t),*)
                   ).collect::<Vec<_>>()
    };
    ($t:ty ;;) => {
        {
            let mut line: String = String::new();
            std::io::stdin().read_line(&mut line).unwrap();
            line.split_whitespace()
                .map(|t| t.parse::<$t>().unwrap())
                .collect::<Vec<_>>()
        }
    };
    ($t:ty ;; $n:expr) => {
        (0..$n).map(|_| get!($t ;;)).collect::<Vec<_>>()
    };
}
const P: i64 = 1000000007;

fn main() {
    let (r, c) = get!(i64, i64);
    let (x, y) = get!(i64, i64);
    let (d, _l) = get!(i64, i64);

    // r行c列のなかにx行y列の長方形を配置する場合の数
    let num = (r - x + 1) * (c - y + 1);

    // (x * y)個の箱に、d個、l個のものを詰める場合の数 = (x * y) C d
    // n C r = n! / r! * (n - r)!
    let c = binomial(x * y, d);

    println!("{}", modulo(num * c));
}

fn binomial(n: i64, r: i64) -> i64 {
    modulo(factorial(n) * modinverse(modulo(factorial(r) * factorial(n - r))))
}

fn factorial(n: i64) -> i64 {
    if n == 0 {
        1
    } else {
        modulo(n * factorial(n - 1))
    }
}

fn modulo(n: i64) -> i64 {
    n % P
}

fn modinverse(a: i64) -> i64 {
    let (_, x, _) = egcd(a, P);
    let i = x % P;
    if i < 0 {
        i + P
    } else {
        i
    }
}

fn egcd(a: i64, b: i64) -> (i64, i64, i64) {
    if a == 0 {
        (b, 0, 1)
    } else {
        let (g, x, y) = egcd(b % a, a);
        (g, y - (b / a) * x, x)
    }
}

Submission Info

Judge Result