random fizz buzz

main.rs

use std::fs::OpenOptions;
use std::io::Write;

use rand::{Rng, SeedableRng};
use rand_pcg::Pcg64;

fn fizz_buzz() -> impl Iterator<Item = String> {
    (1..).map(|i| {
        if i % 15 == 0 {
            "fizzbuzz".to_string()
        } else if i % 3 == 0 {
            "fizz".to_string()
        } else if i % 5 == 0 {
            "buzz".to_string()
        } else {
            i.to_string()
        }
    })
}

fn random_fizz_buzz(seed: u64) -> impl Iterator<Item = String> {
    let mut rng = Pcg64::seed_from_u64(seed);
    let choices = ["fizz", "buzz", "fizzbuzz"];

    (1..).map(move |i| {
        let choice = rng.gen_range(0..4);
        if choice == 3 {
            i.to_string()
        } else {
            choices[choice].to_string()
        }
    })
}

fn match_up_to<T: PartialEq>(reference: impl Iterator<Item = T>, xs: impl Iterator<Item = T>) -> usize {
    reference.zip(xs).take_while(|(r, x)| r == x).count()
}

fn brute_force() {
    let report_file = "report.txt";
    std::fs::remove_file(report_file).unwrap_or(());

    let mut max_so_far = 0;
    for seed in 0u64.. {
        let real_fizz_buzz = fizz_buzz();
        let generated = random_fizz_buzz(seed);
        let up_to = match_up_to(real_fizz_buzz, generated);

        if up_to > max_so_far {
            let mut file = OpenOptions::new()
                .create(true)
                .append(true)
                .open(report_file)
                .unwrap();
            writeln!(file, "{} => {}", seed, up_to).unwrap();
            max_so_far = up_to;
        }
    }
}

fn print_fizz_buzz() -> impl Iterator<Item = String> {
    let mut rng = Pcg64::seed_from_u64(5535459);

    (1..).map(move |i| { ["fizz", "buzz","fizzbuzz", &i.to_string()][rng.gen_range(0..4)].to_string() })
}

fn main() {
    //print_fizz_buzz().take(20).for_each(|i| println!("{}", i));
    brute_force()
}