card-calculator/src/main.rs

use std::collections::HashSet;

use rand::seq::SliceRandom;

#[derive(Clone, Copy, Hash, PartialEq, Eq)]
struct Card {
    color: Color,
    value: u8,
}

impl std::fmt::Debug for Card {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        write!(f, "{}{}", self.color.get_symbol(), self.value)
    }
}

impl Card {
    fn new(color: Color, value: u8) -> Self {
        Self { color, value }
    }

    fn cost(&self) -> u8 {
        match self.color {
            Color::Spades => {
                if self.value == 5 {
                    4
                } else {
                    0
                }
            }
            Color::Hearts => 1,
            _ => 0,
        }
    }
}

#[derive(Clone, Copy, PartialEq, Eq, Hash)]
enum Color {
    Clubs,
    Spades,
    Hearts,
    Diamonds,
}

impl Color {
    fn get_symbol(&self) -> char {
        match self {
            Color::Clubs => '♣',
            Color::Spades => '♠',
            Color::Hearts => '♥',
            Color::Diamonds => '♦',
        }
    }
}

#[derive(Debug)]
enum Knowledge {
    Full(Vec<Card>),
    Partial([bool; 4]),
}

fn solve(
    current: usize,
    knowledge: &[Knowledge],
    unseen: &[Card],
    stack: &mut Vec<Card>,
    remaining: usize,
    played: &mut HashSet<Card>,
) -> Option<(Option<Card>, Vec<f64>)> {
    let num_player = knowledge.len();
    if remaining == 0 {
        Some((None, vec![0.0; num_player]))
    } else if stack.len() == num_player {
        let first_card = stack.first().unwrap();

        let winning_card = stack
            .iter()
            .enumerate()
            .max_by_key(|g| {
                if g.1.color == first_card.color {
                    g.1.value
                } else {
                    0
                }
            })
            .unwrap();

        let winning_player = (current + winning_card.0) % num_player;

        let cost = stack.iter().map(|c| c.cost()).sum::<u8>();

        let mut new_stack = Vec::new();
        if let Some(mut s) = solve(
            winning_player,
            knowledge,
            unseen,
            &mut new_stack,
            remaining - 1,
            played,
        ) {
            s.1[winning_player] += cost as f64;
            Some(s)
        } else {
            None
        }
    } else {
        match &knowledge[current] {
            Knowledge::Full(cards) => {
                if let Some(f) = stack
                    .first()
                    .copied()
                    .filter(|&f| cards.iter().any(|&c| f.color == c.color))
                {
                    let mut min: Option<(Option<Card>, Vec<f64>)> = None;
                    for &c in cards.iter().filter(|&&c| c.color == f.color) {
                        if !played.contains(&c) {
                            stack.push(c);
                            played.insert(c);
                            if let Some(m) = solve(
                                (current + 1) % num_player,
                                knowledge,
                                unseen,
                                stack,
                                remaining,
                                played,
                            ) {
                                if let Some(min) = &mut min {
                                    if m.1[current] < min.1[current] {
                                        *min = (Some(c), m.1);
                                    }
                                } else {
                                    min = Some((Some(c), m.1));
                                }
                            }

                            stack.pop();
                            played.remove(&c);
                        }
                    }
                    min
                } else {
                    let mut min: Option<(Option<Card>, Vec<f64>)> = None;
                    for &c in cards {
                        if !played.contains(&c) {
                            stack.push(c);
                            played.insert(c);

                            if let Some(m) = solve(
                                (current + 1) % num_player,
                                knowledge,
                                unseen,
                                stack,
                                remaining,
                                played,
                            ) {
                                if let Some(min) = &mut min {
                                    if m.1[current] < min.1[current] {
                                        *min = (Some(c), m.1);
                                    }
                                } else {
                                    min = Some((Some(c), m.1));
                                }
                            }

                            stack.pop();
                            played.remove(&c);
                        }
                    }
                    min
                }
            }
            Knowledge::Partial(_) => todo!(),
        }
    }
}

fn main() {
    let mut full_deck = (1..=8)
        .flat_map(|u| {
            [
                Card::new(Color::Clubs, u),
                Card::new(Color::Spades, u),
                Card::new(Color::Hearts, u),
                Card::new(Color::Diamonds, u),
            ]
            .into_iter()
        })
        .collect::<Vec<_>>();

    let mut rng = rand::thread_rng();

    full_deck.shuffle(&mut rng);

    let knowledge = [
        Knowledge::Full(full_deck[0..10].to_vec()),
        Knowledge::Full(full_deck[10..20].to_vec()),
        Knowledge::Full(full_deck[20..30].to_vec()),
    ];

    dbg!(&knowledge);

    let unseen = [];

    let mut stack = Vec::new();
    let mut played = HashSet::new();

    dbg!(solve(0, &knowledge, &unseen, &mut stack, 5, &mut played));
}