projecteuler.net/033/main.rs

fn cancel(n: u32, k: u8) -> u32 {
    let mut res = 0u32;
    let mut ds = Vec::new();
    let mut nn = n;
    while nn > 0 {
        let dd = nn % 10;
        if dd != k as u32 {
            ds.push(nn % 10);
        }
        nn /= 10;
    }
    for x in ds.iter().rev() {
        res *= 10;
        res += x;
    }
    return res;
}

fn gcd(mut a: u32, mut b: u32) -> u32 {
    while b != 0 {
        let remainder = a % b;
        a = b;
        b = remainder;
    }
    a
}

struct Fr {
    n: u32,
    d: u32
}

impl Fr {
    fn from(n: u32, d: u32) -> Fr {
        return Fr { n: n, d: d };
    }
    fn simple(&self) -> Fr {
        let g = gcd(self.n, self.d);
        let n = self.n / g;
        let d = self.d / g;
        return Fr { n: n, d: d };
    }
    fn print(&self) {
        println!("{}/{}", self.n, self.d);
    }
    fn eq(&self, other: &Fr) -> bool {
        let a = self.simple();
        let b = other.simple();
        return a.n == b.n && a.d == b.d;
    }
    fn ds(&self) -> Vec<u8> {
        let mut res = Vec::new();
        let mut n = self.n;
        let mut d = self.d;
        while n > 0 {
            res.push((n % 10) as u8);
            n /= 10;
        }
        while d > 0 {
            res.push((d % 10) as u8);
            d /= 10;
        }
        return res;
    }
    fn cancel(&self, k: u8) -> Fr {
        let n = cancel(self.n, k);
        let d = cancel(self.d, k);
        return Fr{ n: n, d: d };
    }
    fn can_cancel(&self, k: u8) -> bool {
        return cancel(self.n, k) != 0 && cancel(self.d, k) != 0;
    }
    fn test(&self) -> bool {
        let ds = self.ds();
        for k in ds {
            if !self.can_cancel(k) { continue; }
            let cn = self.cancel(k);
            if self.eq(&cn) {
                return true;
            }
        }
        return false;
    }
}

fn main() {
    let mut res_n = 1;
    let mut res_d = 1;
    for n in 10..99 {
        for d in n+1..99 {
            //println!("{}/{}", n, d);
            if n % 10 == 0 && d % 10 == 0 { continue; }
            let f = Fr::from(n, d);
            if f.test() {
                f.print();
                res_n *= n;
                res_d *= d;
            }
        }
    }

    let res_fr = Fr::from(res_n, res_d).simple();
    println!("{}", res_fr.d);

}