====== Tic Tac Toe Game ======
===== Functions =====
^ Function ^ Parameters ^ Return Value ^ Purpose |
| isntr() |None| None | display instructions |
| firstPlayer() | None | goesFirst| selects which piece will move first |
| choosePiece() | None | playerPiece | allows the player to choose a playing piece |
| createBoard() | None | gameBoard | creates a game board |
| displayBoard() | gameBoard | None | prints a game board to the screen |
| legalMoves() | gameBoard | legalMoves | finds/returns a list of legal moves |
| winner() | gameBoard | winner or "TIE" | checks for and returns a winner |
| playerMove() | gameBoard, playerPiece | playerMove | allows player to move and returns space of that move |
| cpuMove() | gameBoard, cpuPiece | cpuMove | allows cpu to move and returns space of that piece |
| nextTurn() | currTurn | nextPiece | selects next piece to move and returns that piece |
| congrats() | winner | None | congratulations the game's winner |

===== Pseudocode =====
==== instr() ====
<code>
print "*insert game instructions here*"
</code>

==== firstPlayer() ====
<code>
select a number between 0 & 1 at random

if the number is 0 then goesFirst is O
otherwise goesFirst is X

return goesFirst
</code>

==== choosePiece() ====
<code>
print "Play as X or O: "
get playerPiece

return playerPiece
</code>

==== createBoard() ====
<code>
board = []

for i from 0 to 9
 append " " to board

return board
</code>

==== displayBoard(gameBoard) ====
<code>
for i from 0 to 9
 print gameBoard[i]
</code>

==== legalMoves(gameBoard) ====
<code>
legalMoves = []
for i from 0 to 9
  if gameBoard[i] == EMPTY
    append gameBoard[i] to legalMoves
return legalMoves
</code>

==== winner(gameBoard) ====
<code>
WINS = ((0, 1, 2), (3, 4, 5), (6, 7, 8),
        (0, 3, 6), (1, 4, 7), (2, 5, 8),
        (0, 4, 8), (2, 4, 6))

for row from 0 to 8
  if gameBoard[row[0]] == gameBoard[row[1]] == gameBoard[row[2]] != " ":
    winner = gameBoard[row[0]]
    return winner
  else if no empty spaces
    return "Tie"
return None
</code>

==== playerMove(gameBoard, playerPiece) ====
<code>
print "Enter a move (0-8): "
get move

while move is not from 0 to 8 and board[move] is not in legalMoves
  print "Enter a move (0-8): "
  get move

return move
</code>

==== cpuMove(gameBoard, cpuPiece) ====
<code>
boardCopy = gameBoard[:]
BEST_MOVES = (4, 0, 2, 6, 8, 1, 3, 5, 7)

print "Taking square"

//If computer can win
for move in legalMoves(boardCopy)
  boardCopy[move] = computer
  if winner(boardCopy) is computer
    print move
    return move
  boardCopy[move] = " "

//if the player can win
for move in legalMoves(boardCopy)
  boardCopy[move] = computer
  if winner(boardCopy) is player
    print move
    return move
  boardCopy[move] = " "

//otherwise no winner pick best square
for move in BEST_MOVES
  if move in legalMoves(boardCopy)
    print move
    return move
    
</code>

==== nextTurn(currTurn) ====
<code>
if currTurn is "X"
  nextTurn = "O"
else
  nextTurn = "X"
return nextTurn
</code>

==== congrats(gameBoard) ====
<code>
if winner(gameBoard) is not "Tie"
  print "Congratulations", winner(gameBoard), "you win!"
else
  "It's a tie!"
</code>