tic tac toe game added

tic_tac_toe/README.md

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+# Tic Tac Toe
+
+Tic Tac Toe is a popular game for two players, X and O, who take turns marking the spaces in a 3×3 grid.
+The player who succeeds in placing three of their marks in a diagonal, horizontal,
+or vertical row is the winner.
+
+For more information about the  the game, check [here](https://en.wikipedia.org/wiki/Tic-tac-toe).
+
+The game was implemented in Python, using **Numpy** library.
+
+## How to launch
+first you need to install *numpy*:\
+`pip install -r requirements.txt`\
+then you can directly launch the main script:\
+`python main.py`
+
+good luck :)
+
+
+#### Game Sample
+each play, in turn, will choose one of the available positions by
+entering the corresponding number. Numbers are 0-8 from going from top-left
+to bottom-right corner.
+
+*start*
+
+![Start](media/start.JPG)
+
+*first move*
+
+![first-move](media/first-move.JPG)
+
+*winner*
+
+![winner](media/winner.JPG)

tic_tac_toe/main.py

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+import numpy as np
+
+
+grid = np.full((3,3), '-')
+cells = {'0': (0,0), '1': (0,1), '2': (0,2),
+         '3': (1,0), '4': (1,1), '5': (1,2),
+         '6': (2,0), '7': (2,1), '8': (2,2)}
+
+diagonal_1 = [0,1,2], [0,1,2]  # main diagonal
+diagonal_2 = [0,1,2], [2,1,0]  # reverse diagonal
+ver_hor_lines = {'v1': grid[:,0], 'v2': grid[:,1], 'v3': grid[:,2],  # verticals
+                 'h1': grid[0,:], 'h2': grid[1,:], 'h3': grid[2,:]}  # horizontals
+
+player = ''
+turn = 1
+free_spots = ['0', '1', '2', '3', '4', '5', '6', '7', '8']
+spot = ''
+
+while True:
+    # printing the grid
+    for el in grid:
+        print('  '.join(el.astype(str)))
+
+    # check if player won
+    if np.all(grid[diagonal_1] == player) or np.all(grid[diagonal_2] == player):
+        print(f"player {player.upper()}, you won !")
+        quit()
+    for line in ver_hor_lines:
+        if np.all(ver_hor_lines[line] == player):
+            print(f"player {player.upper()}, you won !")
+            quit()
+    print('available positions: {}'.format(' '.join(free_spots)))
+
+    # check if game ended as a tie
+    if not free_spots:
+        print('END GAME: TIE')
+        break
+
+    # update the player
+    if turn % 2 == 0:
+        player = 'o'
+    else:
+        player = 'x'
+
+    # ask the input
+    spot = input('player {}, enter a position: '.format(player.upper()))
+    # entering 'out' will end the game at anytime
+    if spot == 'out':
+        quit()
+    # check if input is valid
+    if spot in free_spots:
+        # update the grid
+        position = cells[spot]
+        grid[position] = player
+        free_spots.remove(spot)
+        turn += 1
+    else:
+        print('not valid. Enter again.')
+
+    print()

tic_tac_toe/requirements.txt

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+numpy==1.19.4