day2.rs

use std::i32::MAX;

use itertools::Itertools;
use num::abs;

use crate::{DaySolution, FromInput};

// TODO: Model the problem into this struct
pub struct Day2 {
    reports: Vec<Vec<i32>>,
}

impl FromInput for Day2 {
    fn from_lines(_lines: impl Iterator<Item = String>) -> Self {
        let mut reports = vec![];
        for l in _lines {
            let x: Vec<i32> = l
                .split(" ")
                .into_iter()
                .map(|a| i32::from_str_radix(a, 10).unwrap())
                .collect_vec();
            reports.push(x);
        }

        Day2 { reports }
    }
}

fn is_increasing(v: &Vec<i32>) -> bool {
    let mut last = -1;
    for e in v {
        if *e <= last {
            return false;
        }
        last = *e;
    }
    true
}

fn is_decreasing(v: &Vec<i32>) -> bool {
    let mut last = MAX;
    for e in v {
        if *e >= last {
            return false;
        }
        last = *e;
    }
    true
}

fn diff_check(v: &Vec<i32>, threshold: i32) -> bool {
    let mut last = v[0];
    for e in v {
        if abs(e - last) > threshold {
            return false;
        }
        last = *e;
    }
    true
}

fn check_slice(r: &Vec<i32>) -> bool {
    if is_increasing(r) || is_decreasing(r) {
        if diff_check(r, 3) {
            return true;
        }
    }
    false
}

fn check_subsets(v: &Vec<i32>) -> bool {
    if check_slice(v) {
        return true;
    }

    for i in 0..v.len() {
        let all = [&v[..i], &v[i + 1..]].concat();

        if is_increasing(&all) || is_decreasing(&all) {
            if diff_check(&all, 3) {
                return true;
            }
        }
    }
    false
}

impl DaySolution for Day2 {
    fn part_one(&self) -> String {
        let mut sum = 0_usize;

        for r in &self.reports {
            if check_slice(r) {
                sum += 1;
            }
        }

        sum.to_string()
    }

    fn part_two(&self) -> String {
        let mut sum = 0_usize;
        for r in &self.reports {
            if check_subsets(r) {
                sum += 1;
            }
        }
        sum.to_string()
    }
}