0794. Valid Tic-Tac-Toe State

https://leetcode.com/problems/valid-tic-tac-toe-state

Description

Given a Tic-Tac-Toe board as a string array board, return true if and only if it is possible to reach this board position during the course of a valid tic-tac-toe game.

The board is a 3 x 3 array that consists of characters ' ', 'X', and 'O'. The ' ' character represents an empty square.

Here are the rules of Tic-Tac-Toe:

• Players take turns placing characters into empty squares ' '.

• The first player always places 'X' characters, while the second player always places 'O' characters.

• 'X' and 'O' characters are always placed into empty squares, never filled ones.

• The game ends when there are three 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.

Example 1:

**Input:** board = ["O  ","   ","   "]
**Output:** false
Explanation: The first player always plays "X".

Example 2:

**Input:** board = ["XOX"," X ","   "]
**Output:** false
Explanation: Players take turns making moves.

Example 3:

**Input:** board = ["XXX","   ","OOO"]
**Output:** false

Example 4:

**Input:** board = ["XOX","O O","XOX"]
**Output:** true

Constraints:

• board.length == 3

• board[i].length == 3

• board[i][j] is either 'X', 'O', or ' '.

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