adventofcode2021/day04/part1.nim

# Copyright 2021 Christian Ulrich
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.

# usage: ./part1 < input

import sequtils
import strutils

type
  Board = array[5, array[5, int8]]

iterator lines(board: Board): array[5, int8] =
  for i in 0 .. high(Board):
    yield board[i]

iterator columns(board: Board): array[5, int8] =
  for i in 0 .. high(board[0]):
    var column: array[5, int8]
    for j in 0 .. high(Board):
      column[j] = board[j][i]
    yield column

proc check(board: var Board, val: int8) =
  for i in 0 .. high(Board):
    for cellIndex, cell in board[i].pairs():
      if cell == val:
        board[i][cellIndex] = -1

proc readDrawnNumbers(): seq[int8] =
  result = readLine(stdin).split(',').mapIt(int8(parseUint(it)))

proc readBoards(): seq[Board] =
  var
    line: string
    board: Board
  while true:
    if not readLine(stdin, line):
      return
    for i in 0 .. high(Board):
      if not readLine(stdin, line):
        return
      board[i][0 .. high(Board)] = line.splitWhitespace(4)
                                       .mapIt(int8(parseUint(it)))
    result.add(board)

proc bingoScore(board: Board, latestNumber: int8): int =
  var unmarkedSum = 0
  for line in board.lines():
    unmarkedSum.inc(line.foldl(if b >= 0: a + int(b) else: a, 0))
  result = unmarkedSum * int(latestNumber)

proc bingo(): int =
  let drawnNumbers = readDrawnNumbers()
  var boards = readBoards()
  for number in drawnNumbers:
    for board in boards.mitems():
      board.check(number)
      for line in board.lines():
        if line.allIt(it < 0):
          return board.bingoScore(number)
      for column in board.columns():
        if column.allIt(it < 0):
          return board.bingoScore(number)
  raise newException(ValueError, "there is no winner")

proc main(): int =
  try:
    echo bingo()
  except Exception as error:
    echo error.msg
    result = -1

when isMainModule:
  quit(main())