advent-of-code-2023-rust/src/day7.rs

use std::{fmt::Display, cmp::Ordering};

use itertools::Itertools;

use crate::day_solver::DaySolver;
#[cfg(test)]
use crate::util::read_file;

const CARD_ORDER: [char; 13] = ['A', 'K', 'Q', 'J', 'T', '9', '8', '7', '6', '5', '4', '3', '2'];

pub struct Day7 {
    hands: Vec<Hand>
}

pub struct Hand {
    cards: [char; 5],
    bid: usize
}

impl Display for Hand {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        write!(f, "{} {}", self.cards.iter().collect::<String>(), self.bid)
    }
}

impl Hand {
    fn parse(input: &str) -> Self {
        let (cards_str, bid_str) = input.split_once(" ").unwrap();
        return Hand {
            cards: cards_str.chars().collect::<Vec<char>>().try_into().unwrap(),
            bid: bid_str.parse().unwrap()
        }
    }

    fn calc_type(&self) -> u8 {
        let mut found_three_of_kind = false;
        let mut found_pair = false;
        for unique_card in self.cards.iter().unique() {
            let card_appearances = self.cards.iter().filter(|c| c == &unique_card).count();
            if card_appearances == 5 {
                return FIVE_OF_A_KIND;
            } else if card_appearances == 4 {
                return FOUR_OF_A_KIND;
            } else if card_appearances == 3 {
                found_three_of_kind = true;
            } else if card_appearances == 2 {
                if found_pair {
                    return TWO_PAIR
                } else {
                    found_pair = true
                }
            }
        }
        if found_three_of_kind && found_pair {
            return FULL_HOUSE;
        } else if found_three_of_kind {
            return THREE_OF_A_KIND;
        } else if found_pair {
            return ONE_PAIR;
        }
        return HIGH_CARD;
    }

    // Calculates the maximum type, given that "J" is a joker
    fn calc_max_type(&self) -> u8 {
        if !self.cards.contains(&'J') {
            return self.calc_type();
        }

        let mut max_type = self.calc_type();
        if max_type == FIVE_OF_A_KIND { return max_type };

        // It only makes sense to try to map jokers to any of the other cards we have
        let owned_cards: Vec<&char> = self.cards.iter().filter(|c| c != &&'J').unique().collect();
        for i in 0..5 {
            if self.cards[i] == 'J' {
                for c in &owned_cards {
                    let mut new_cards = self.cards.clone();
                    new_cards[i] = *c.to_owned();
                    let new_hand = Hand { cards: new_cards, bid: 0};
                    let j_type = new_hand.calc_max_type();
                    // println!("Trying hand {} as {}, got type {}", self, new_hand, j_type);
                    if j_type > max_type {
                        max_type = j_type;
                        if max_type == FIVE_OF_A_KIND { return max_type }
                    }
                }
            }
        }
        return max_type;
    }
}

const FIVE_OF_A_KIND: u8 = 64;
const FOUR_OF_A_KIND: u8 = 32;
const FULL_HOUSE: u8 = 16;
const THREE_OF_A_KIND: u8 = 8;
const TWO_PAIR: u8 = 4;
const ONE_PAIR: u8 = 2;
const HIGH_CARD: u8 = 0;

impl Day7 {

    pub fn create(input: String) -> Self {
        // let lines = input.lines();

        // Put the input into the day struct
        return Day7 {
            hands: input.lines().map(Hand::parse).collect()
        }
    }
}

fn card_rank(card: &char) -> usize {
    for i in 0..CARD_ORDER.len() {
        if &CARD_ORDER[i] == card {
            return i;
        }
    }
    CARD_ORDER.len()
}

fn compare_card(a: &char, b: &char) -> Ordering {
    return card_rank(b).partial_cmp(&card_rank(a)).unwrap();
}

fn compare_card_pt2(a: &char, b: &char) -> Ordering {
    if a == &'J' && b == &'J' { return Ordering::Equal }
    else if a == &'J' { return Ordering::Less }
    else if b == &'J' { return Ordering::Greater }
    else {
        return card_rank(b).partial_cmp(&card_rank(a)).unwrap();
    }
}

impl DaySolver for Day7 {


    fn solve_part1(&mut self) -> String {
        let mut hands_and_types: Vec<(&Hand, u8)> = self.hands.iter()
            .map(|h| (h, h.calc_type()))
            .collect();
        hands_and_types.sort_by(|a, b| {
            if a.1 != b.1 {
                return a.1.partial_cmp(&b.1).unwrap();
            } else {
                for i in 0usize..5 {
                    let card_comp = compare_card(&a.0.cards[i], &b.0.cards[i]);
                    if card_comp.is_ne() {
                        return card_comp;
                    }
                }
                return Ordering::Equal;
            }
        });
        return hands_and_types.iter().map(|(h,_)|h).enumerate()
            .map(|(r, h)| (r + 1) * h.bid)
            .sum::<usize>()
            .to_string();
    }

    fn solve_part2(&mut self) -> String {
        let mut hands_and_max_types: Vec<(&Hand, u8)> = self.hands.iter()
            .map(|h| (h, h.calc_max_type()))
            .collect();
        hands_and_max_types.sort_by(|a, b| {
            if a.1 != b.1 {
                return a.1.partial_cmp(&b.1).unwrap();
            } else {
                for i in 0..5 {
                    let card_comp = compare_card_pt2(&a.0.cards[i], &b.0.cards[i]);
                    if card_comp.is_ne() {
                        return card_comp;
                    }
                }
                return Ordering::Equal;
            }
        });
        // for (hand, max_type) in &hands_and_max_types {
        //     println!("Hand {} with type {}", hand, max_type);
        // }
        return hands_and_max_types.iter().map(|(h,_)|h).enumerate()
            .map(|(r, h)| (r + 1) * h.bid)
            .sum::<usize>()
            .to_string();
    }
}

#[test]
fn test_part1() {
    let mut day = Day7::create(read_file("input/day07_example.txt"));
    assert_eq!("6440", day.solve_part1());
}

#[test]
fn test_part2() {
    let mut day = Day7::create(read_file("input/day07_example.txt"));
    assert_eq!("5905", day.solve_part2());
}