aoc.rs

fn main() {
    let n = usize::MAX/10;
    println!("Part 1");
    println!("Q: {}, A: {}", n, steal_from_left(n));
    println!("Part 2");
    println!("Q: {}, A: {}", n, steal_across(n));
}
/*
OUTPUT: 

Part 1
Q: 1844674407370955161, A: 1383505805528216371
Part 2
Q: 1844674407370955161, A: 493822689697963072
*/

fn steal_from_left(n: usize) -> usize {
    return match n {
        x if x <= 2 => 1,
        x if is_odd(x) => steal_from_left(n / 2) * 2 + 1,
        _ => (steal_from_left(n / 2) - 1) * 2 + 1
    };
}

fn steal_across(n: usize) -> usize {
    let mut base = 1;
    let mut limit = 3;
    while n > limit {
        base = limit;
        limit *= 3;
    }
    return half_dist(n-base, limit-base);
}

fn half_dist(i: usize, n: usize) -> usize {
    if i <= n / 2 { 
        i 
    } else { 
        (i - n / 2) * 2 + n / 2 
    }
}