Valid TicTacToe State
We can create a function to validate a TicTacToe board by observing some constraints:
 The number of
X
’s must be equal to or one more than the number of O
’s.  If there are three
X
’s in a row, then the number of X
’s must be one more than the number of O
’s.  If there are three
O
’s in a row, then the number of X
’s must be equal to the number of O
’s.  There can’t be three
X
’s and three O
’s in a row at the same time.
Here’s a code that implements these constraints:
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 class Solution:
def validTicTacToe(self, board: List[str]) > bool:
# Counting the number of 'X' and 'O'
xCount = oCount = 0
for row in board:
for cell in row:
if cell == 'X':
xCount += 1
elif cell == 'O':
oCount += 1
# Function to check if a player has won
def win(player: str) > bool:
# Check rows, columns, and diagonals
for i in range(3):
if all(board[i][j] == player for j in range(3)) or \
all(board[j][i] == player for j in range(3)):
return True
return board[0][0] == board[1][1] == board[2][2] == player or \
board[0][2] == board[1][1] == board[2][0] == player
# Validate the board
xWin = win('X')
oWin = win('O')
if (xWin and xCount != oCount + 1) or \
(oWin and xCount != oCount) or \
(xCount < oCount or xCount > oCount + 1) or \
(xWin and oWin):
return False
return True

This code checks for the constraints described above, returning True
if the board is valid and False
otherwise. It counts the occurrences of X
and O
, checks for winning conditions, and then validates the board based on the constraints of a valid TicTacToe game.