public class Solution
extends Object
794 - Valid Tic-Tac-Toe State\.
Medium
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 = ["XOX","O O","XOX"]
**Output:** true
**Constraints:**
* `board.length == 3`
* `board[i].length == 3`
* `board[i][j]` is either `'X'`, `'O'`, or `' '`.