d5.rs

use std::fs::File;
use std::io::Read;

fn main() {
    let mut f = File::open("d5.in").expect("input file not found");

    let mut s = String::new();
    f.read_to_string(&mut s).unwrap();

    let mut v: Vec<isize> = s.split("\n")
                             .filter(|s| s != &"")
                             .map(|s| s.parse::<isize>().unwrap())
                             .collect();

    let mut c = 0;
    let mut idx = 0;

    while idx >= 0 && idx < v.len() as isize {
        let ni = idx + v[idx as usize];

        v[idx as usize] += if v[idx as usize] < 3 {
            1
        } else {
            -1
        };

        idx = ni;
        c += 1;
    }

    println!("{}", c);
}