give-a-dollar.rs

// give.a.dollar.rs, from julia, from tiny-c:
// http://primepuzzle.com/not.just.tiny.c/give.a.dollar.try.tc?fbclid=IwAR2p5YBQgJJDY3-g3lN3rRHw7v7cA0VB0BcNWv4dHybH-XCCgxQQIrbF6sY
// ref: https://www.facebook.com/groups/299317782048/posts/10160467717107049/
use std::io;
use rand::prelude::*;
use timed::timed; //https://y2kappa.github.io/blog/posts/timing-your-function-execution/

fn gn() -> i32 {
    let mut input = String::new();
    match io::stdin().read_line(&mut input) {
        Ok(_n_size) => {
            let n : i32 = input.trim().parse::<i32>().unwrap();
            return n;
        }
        Err(error) => {
            println!("error: {error}");
            return 0;
        }
    }
}

#[timed]
fn givadollar(limit : i32) -> () {
    let mut rng = thread_rng();
    let mut dollar = vec![45 as i32; 45];
    for _j in 0..limit {
        for i in 0..45 { 
            if dollar[i] > 0 { // can't give if you don't have
                let mut rn = rng.gen_range(0..=43);
                if rn >= i {
                    rn+=1;
                }
                dollar[rn]+=1; // # give a random person $1
                dollar[i]-=1; // and deduct $1 from the giver
            }
        } // i
    } // j
    for i in 0..45 { // display results
        print!("{:3} ", dollar[i]);
    }
}

fn main() {

    println!("give-a-dollar TC version by lrb - 9/3/22 -- translation to Rust by AWW 9/8/22");
    let mut limit = 0;
    //let mut seed = 0; // dont feel like learning how to use SeedableRng
    if limit == 0 {
        print!("number of rounds, e.g. 50..10000 : ");
        limit = gn();
        // print!("seed please (0 for no seed) : ");
        // let seed = gn();
        // if seed != 0 {
        // }        
    }
    givadollar(limit);
}