AoC 2023 day 9

fn main() {
    let input = std::fs::read_to_string("../inputs/input.txt").unwrap();
    let mut lines: Vec<Vec<i32>> = input
        .lines()
        .map(|line| {
            line.split_whitespace()
                .map(|n| n.parse::<i32>().unwrap())
                .collect()
        })
        .collect();

    println!("part 1: {}", solve(&lines));
    lines.iter_mut().for_each(|v| v.reverse());
    println!("part 2: {}", solve(&lines));
}

fn solve(lines: &[Vec<i32>]) -> i32 {
    let mut sum = 0;
    for numbers in lines.iter() {
        let mut all_steps: Vec<Vec<i32>> = Vec::new();
        let mut new_numbers = numbers.clone();
        all_steps.push(new_numbers.clone());

        while !new_numbers.iter().all(|&x| x == 0) {
            let mut current_numbers = Vec::with_capacity(new_numbers.len());
            for win in new_numbers.windows(2) {
                let diff = win[1] - win[0];
                current_numbers.push(diff);
            }
            new_numbers = current_numbers;
            all_steps.push(new_numbers.clone());
        }
        let mut prev_line: Option<Vec<i32>> = None;

        for step_line in all_steps.iter_mut().rev() {
            if let Some(prev_line) = prev_line {
                let last = step_line.last().unwrap();
                let prev_last = prev_line.last().unwrap();
                step_line.push(last + prev_last);
            } else {
                step_line.push(0);
            }
            prev_line = Some(step_line.clone());
        }

        let res = all_steps.first().unwrap().last().unwrap();
        sum += res;
    }
    sum
}