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g0701_0800.s0794_valid_tic_tac_toe_state.readme.md Maven / Gradle / Ivy

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:**

![](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/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 `' '`.