How to find first winning combination in Tic-Tac-Toe board? - ruby

Question

New at Ruby so excuse the poor code. I would like to iterate through the multidimensional array WIN_COMBINATIONS and check whether at least one array has all of its elements equal to 'X' or all equal to 'O'. If so, return the matched array. This is done through the won? function but it seems to only be returning the entire multidimensional array. Any assistance would be appreciated.
class TicTacToe
WIN_COMBINATIONS = [
[0,1,2], # top_row
[3,4,5], # middle_row
[6,7,8], # bottom_row
[0,3,6], # left_column
[1,4,7], # center_column
[2,5,8], # right_column
[0,4,8], # left_diagonal
[6,4,2] # right_diagonal
]
def initialize
#board = Array.new(9, " ")
end
def display_board
puts " #{#board[0]} | #{#board[1]} | #{#board[2]} "
puts "-----------"
puts " #{#board[3]} | #{#board[4]} | #{#board[5]} "
puts "-----------"
puts " #{#board[6]} | #{#board[7]} | #{#board[8]} "
end
def input_to_index(board_position)
user_input = board_position.to_i
user_input - 1
end
def move(board_index, player_token = 'X')
#board[board_index] = player_token
end
def position_taken?(board_position)
if #board[board_position] == ' '
false
else
true
end
end
def valid_move?(board_position)
if board_position >= 0 and board_position <= 8
if #board[board_position] == ' '
true
end
else
false
end
end
def current_player
turn_count % 2 == 0 ? "X" : "O"
end
def turn_count
#board.count{|token| token == "X" || token == "O"}
end
def turn
puts "Select your move (1-9)\n"
move = gets.chomp
move_index = input_to_index(move)
if valid_move?(move_index)
token = current_player
move(move_index, token)
display_board
else
puts "Select your move (1-9)\n"
move = gets.chomp
end
end
def won?
WIN_COMBINATIONS.each do |combinations|
if combinations.all? {|combination| combination == 'X' or combination == 'O'}
combinations
else
false
end
end
end
def draw?
if full? and !won?
true
elsif won?
false
else
false
end
end
def over?
end
def winner
end
def play
end
end

Answer 1

[...] it seems to only be returning the entire multidimensional array.
There are several issues with your attempted solution:
WIN_COMBINATIONS is an array of indices. These indices are numeric, so they will never be 'X' or 'O'. You have to check whether their corresponding values are 'X' or 'O'.
or is a control-flow operator intended for do_this or fail scenarios. The boolean "or" operator is ||. Using or instead of || might work but may have unexpected results due to its lower precedence. You almost always want ||.
The expression array.all? { |element| element == 'X' || element == 'O' } checks whether all elements are either 'X' or 'O'. It would be true for ['X','O','O'] and false for ['X',' ','O']. That's because you put the conditional inside the block. What you want is to check whether the elements are all 'X', or all 'O':
array.all?('X') || array.all?('O')
Your method's return value is the result of WIN_COMBINATIONS.each { ... } and Array#each always returns the array itself (i.e. WIN_COMBINATIONS) regardless of the blocks' result. To get the first element matching a condition, use find.
Let's apply all this to your code. Given this board:
#board = %w[
X - O
O X -
- - X
]
You could get the first matching combination via:
WIN_COMBINATIONS.find do |indices|
values = #board.values_at(*indices)
values.all?('X') || values.all?('O')
end
#=> [0, 4, 8]
values_at returns the values for the corresponding indices (* transforms the indices array to a list of arguments, so values_at(*[0,1,2]) becomes values_at(0,1,2)). The block's 2nd line then checks whether these values are all 'X', or all 'O'. Once this evaluates to true, the loop breaks and find returns the matching element. (or nil if there was no match)

Answer 2

Here is how I would approach the problem:
class TicTacToe
class OccupiedError < StandardError; end
attr_reader :rows
def initialize
#rows = 3.times.map{ Array(3, nil) }
end
def place!(player, x:, y:)
raise ArgumentError, "player must be :x or :o" unless [:x, :o].include?(player)
raise OccupiedError, "slot is already occupied" unless #rows[y][x].nil?
#rows[y][x] = player
end
# gets an array of columns instead of rows.
def columns
(0..2).map { |n| #rows.map {|row| row[n] } }
end
def diagonals
[
[#rows[0][0], #rows[1][1], #rows[2][2]], # lrt
[#rows[0][2], #rows[1][1], #rows[2][0]] # rtl
]
end
def all_combos
rows + columns + diagonals
end
# checks all the horizontal, vertical and diagonal combinations
def check_for_winner
# checks all combos for three in a row
(all_combos.find{ |a| a.all?(:x) || a.all?(:o) })&.first
end
end
In the initialize method we create a 3*3 array which represents all the positions on the board. This makes it a lot easier since its already grouped in rows. Intead of an empty string use nil to represent an empty square as nil is falsy.
When we want to check for a winner we gather up the rows, columns and the two diagonals into an array of arrays:
[1] pry(main)> game.rows
=> [[:o, :o, :o], [nil, :x, :x], [:x, nil, nil]]
[2] pry(main)> game.all_combos
=> [[:o, :o, :o],
[nil, :x, :x],
[:x, nil, nil],
[:o, nil, :x],
[:o, :x, nil],
[:o, :x, nil],
[:o, :x, nil],
[:o, :x, :x]]
From there we just have to check if any of them are all :x or :o. We don't actually have to list the winning combinations. In this case game.check_for_winner will return :o.