fish.csv

fish_puzzle.rb

require 'csv'

def permute(input)
  if input.length == 2
    [
      [input[0], input[1]],
      [input[1], input[0]]
    ]
  else
    input.inject([]) do |output, elem|
      list = input.clone
      list.delete(elem)
      output + permute(list).map {|l| l.unshift(elem)}
    end
  end
end

def solve(guess)
  solution = []
  HEIGHT.times {solution << []}
  solved = solve_r(0, 0, guess, solution, [])
  solved && solution
end


def solve_r(row, col, guess, solution, used)
  return true if used.length == NUM_CARDS
  fish = guess[SQUARE[row][col] - 1]
  CARD_GROUPS[fish].each do |card|
    next if used.include? card
    next if solution[row][col - 1][E] != card[W] if col > 0
    next if solution[row - 1][col][S] != card[N] if row > 0
    solution[row][col] = card
    used << card
    if col == WIDTH - 1
      next_col = 0
      next_row = row + 1
    else
      next_col = col + 1
      next_row = row
    end
    solved = solve_r(next_row, next_col, guess, solution, used)
    if solved
      return true
    else
      used.delete(card)
    end
  end
  false
end

F = 0
N = 1
W = 2
S = 3
E = 4

CARDS = CSV.read('fish.csv')

NUM_CARDS = CARDS.length

CARD_GROUPS = CARDS.group_by {|c| c[F]}

OPTS = CARD_GROUPS.keys

SQUARE = CSV.read('magic_square.csv', converters: :numeric)

WIDTH = HEIGHT = SQUARE.length

GUESSES = permute(OPTS)

GUESSES.each do |g|
  solution = solve(g)
  if solution
    solution.each do |row|
      puts row.map {|c| c.join('').upcase}.join(' ')
    end
    break
  end
end

magic_square.csv