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# 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:**

![](https://assets.leetcode.com/uploads/2021/05/15/tictactoe1-grid.jpg)

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

**Example 2:**

![](https://assets.leetcode.com/uploads/2021/05/15/tictactoe2-grid.jpg)

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

**Example 3:**

![](https://assets.leetcode.com/uploads/2021/05/15/tictactoe3-grid.jpg)

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

**Example 4:**

![](https://assets.leetcode.com/uploads/2021/05/15/tictactoe4-grid.jpg)

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

**Constraints:**

* `board.length == 3`
* `board[i].length == 3`
* `board[i][j]` is either `'X'`, `'O'`, or `' '`.

## ac

```java
```