advent-of-code/source/year_2021/day_04/board.rs

//! [`Board`] code and implementation.

use std::str::FromStr;

use color_eyre::eyre::Error;

/// A matrix of all the indexes that constitute a win.
const WIN_MATRIX: &[&[usize]] = &[
  // Horizontal lines
  &[0, 1, 2, 3, 4],
  &[5, 6, 7, 8, 9],
  &[10, 11, 12, 13, 14],
  &[15, 16, 17, 18, 19],
  &[20, 21, 22, 23, 24],
  // Vertical lines
  &[0, 5, 10, 15, 20],
  &[1, 6, 11, 16, 21],
  &[2, 7, 12, 17, 22],
  &[3, 8, 13, 18, 23],
  &[4, 9, 14, 19, 24],
];

/// A single bingo board.
#[derive(Debug, Clone)]
pub struct Board {
  /// Whether this board has at least one line filled.
  pub has_won: bool,
  /// The state of the board, with indexes determining the position and whether
  /// that position has been filled.
  pub state: Vec<(i32, bool)>,
}

impl Board {
  /// Create a new board from a set of numbers.
  pub fn new(numbers: Vec<i32>) -> Self {
    Self {
      has_won: false,
      state: numbers.into_iter().map(|number| (number, false)).collect(),
    }
  }

  /// Check whether a board has won.
  pub fn check(&self) -> bool {
    for indexes in WIN_MATRIX {
      if indexes.iter().all(|index| {
        *self
          .state
          .get(*index)
          .map(|(_, state)| state)
          .unwrap_or(&false)
      }) {
        return true;
      }
    }

    false
  }

  /// Marks a target number as true in the board's state.
  pub fn mark_number(&mut self, target: i32) {
    if let Some(entry) = self.state.iter_mut().find_map(|(number, state)| {
      if number == &target {
        Some(state)
      } else {
        None
      }
    }) {
      *entry = true;
    }
  }

  /// Returns the sum of all numbers that haven't been marked as true.
  pub fn sum_unmarked(self) -> i32 {
    self
      .state
      .into_iter()
      .filter_map(|(number, state)| if !state { Some(number) } else { None })
      .sum()
  }
}

impl FromStr for Board {
  type Err = Error;

  fn from_str(s: &str) -> Result<Self, Self::Err> {
    let numbers = s
      .replace('\n', " ")
      .split(' ')
      .filter(|s| s != &"")
      .map(str::parse)
      .collect::<Result<_, _>>()?;

    Ok(Self::new(numbers))
  }
}