Code shared from the Rust Playground

playground.rs

fn factorize(mut composite: u64) -> Vec<u64> {
    let mut factors: Vec<u64> = Vec::new();
    while composite % 2 == 0 {
        composite /= 2;
        factors.push(2);
    }
    let mut f = 3;
    while f * f <= composite {
        if composite % f == 0 {
            factors.push(f);
            composite /= f;
        } else {
            f += 2;
        }
    }
    if composite != 1 {
        factors.push(composite);
    }
    return factors
}

fn foobar(composite: u64) -> String{
    let factors = factorize(composite);
    let mut reply: String = "`".to_string();
    if factors.len() > 1 {
        let mut cur_factor: &u64 = factors.first().unwrap();
        let mut times_repeated = 1;
        for i in factors.iter().skip(1) {
            if i != cur_factor {
                if times_repeated != 1 {
                    reply.push_str(&format!(" {}^{} *", cur_factor, times_repeated));
                    times_repeated = 1;
                } else {
                    reply.push_str(&format!(" {} *", cur_factor));
                }
                cur_factor = i;
            } else {
                times_repeated += 1;
            }
        }
        if composite != 1 {
            reply.push_str(&format!(" {}`", composite));
        } else {
            let len = reply.len() - 2;
            reply.truncate(len);
            reply.push('`');
        }
    } else {
         reply = format!("`{} is a prime number`",factors.first().unwrap());
    }
    reply
}


fn main(){
    println!("{}", foobar(25))
}