Merge pull request #160 from codeconnector/add-2021-09-21-challenge

Add 2021 09 21 challenge

challenges/2021-09-20-tic-tac-toe-winner/challenge.md

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+# Find Winner on a Tic Tac Toe Game
+
+Tic-tac-toe is played by two players A and B on a 3 x 3 grid.
+
+Here are the rules of Tic-Tac-Toe:
+
+Players take turns placing characters into empty squares `(" ")`.
+The first player A always places "X" characters, while the second player B always places "O" characters.
+"X" and "O" characters are always placed into empty squares, never on filled ones.
+The game ends when there are 3 of the same (non-empty) character filling any row, column, or diagonal.
+The game also ends if all squares are non-empty.
+No more moves can be played if the game is over.
+Given an array moves where each element is another array of size 2 corresponding to the row and column of the grid where they mark their respective character in the order in which A and B play.
+
+Return the winner of the game if it exists (`A` or `B`), in case the game ends in a draw return `"Draw"`, if there are still movements to play return `"Pending"`.
+
+You can assume that moves is valid (It follows the rules of Tic-Tac-Toe), the grid is initially empty and A will play first.
+
+
+
+### Example 1:
+
+```
+Input: moves = [[0,0],[2,0],[1,1],[2,1],[2,2]]
+Output: "A"
+Explanation: "A" wins, he always plays first.
+
+[X][ ][ ]
+[ ][ ][ ]
+[ ][ ][ ]
+
+[X][ ][ ]
+[ ][ ][ ]
+[O][ ][ ]
+
+[X][ ][ ]
+[ ][X][ ]
+[O][ ][ ]
+
+[X][ ][ ]
+[ ][X][ ]
+[O][O][ ]
+
+[X][ ][ ]
+[ ][X][ ]
+[O][O][X]
+```
+
+### Example 2:
+```
+Input: moves = [[0,0],[1,1],[0,1],[0,2],[1,0],[2,0]]
+Output: "B"
+Explanation: "B" wins.
+
+[X][X][O]
+[X][O][ ]
+[O][ ][ ]
+```
+
+### Example 3:
+
+```
+Input: moves = [[0,0],[1,1],[2,0],[1,0],[1,2],[2,1],[0,1],[0,2],[2,2]]
+Output: "Draw"
+Explanation: The game ends in a draw since there are no moves to make.
+
+[X][X][O]
+[O][O][X]
+[X][O][X]
+```
+
+### Example 4:
+
+```
+Input: moves = [[0,0],[1,1]]
+Output: "Pending"
+Explanation: The game has not finished yet.
+[X][ ][ ]
+[ ][O][ ]
+[ ][ ][ ]
+```
+
+
+### Constraints:
+
+```
+1 <= moves.length <= 9
+moves[i].length == 2
+0 <= moves[i][j] <= 2
+There are no repeated elements on moves.
+moves follow the rules of tic tac toe.
+```
+
+### Prerequisites
+
+Ruby > 2.0
+
+[bundler](https://bundler.io/)
+
+
+From the `solutions/ruby` folder with
+```
+bundle install
+
+# run the tests with
+ruby -I lib:test tic_tac_test.rb --verbose
+```

challenges/2021-09-20-tic-tac-toe-winner/solutions/ruby/Gemfile

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+# frozen_string_literal: true
+
+source "https://rubygems.org"
+
+gem 'minitest'

challenges/2021-09-20-tic-tac-toe-winner/solutions/ruby/Gemfile.lock

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+GEM
+  remote: https://rubygems.org/
+  specs:
+    minitest (5.14.4)
+    rake (13.0.6)
+
+PLATFORMS
+  ruby
+
+DEPENDENCIES
+  minitest
+  rake
+
+BUNDLED WITH
+   2.1.4

challenges/2021-09-20-tic-tac-toe-winner/solutions/ruby/mob.rb

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+# frozen_string_literal: true
+
+def who_wins(board)
+
+end

challenges/2021-09-20-tic-tac-toe-winner/solutions/ruby/tic_tac_test.rb

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+# frozen_string_literal: true
+
+require 'minitest/autorun'
+require './mob'
+
+describe 'who_wins' do
+  it 'returns the winner of board1' do
+    board1 = [[0, 0], [2, 0], [1, 1], [2, 1], [2, 2]]
+
+    _(who_wins(board1)).must_equal 'A'
+  end
+
+  it 'returns the winner for board2' do
+    board2 = [[0, 0], [1, 1], [0, 1], [0, 2], [1, 0], [2, 0]]
+
+    _(who_wins(board2)).must_equal 'B'
+  end
+
+  it "returns 'Draw' for board3" do
+    board3 = [[0, 0], [1, 1], [2, 0], [1, 0], [1, 2], [2, 1], [0, 1], [0, 2], [2, 2]]
+
+    _(who_wins(board3)).must_equal 'Draw'
+  end
+
+  it "returns 'Pending' for board4" do
+    board4 = [[0, 0], [1, 1]]
+
+    _(who_wins(board4)).must_equal 'Pending'
+  end
+end