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Check Validity of Tic-Tac-Toe Board

Explore how to validate the state of a tic tac toe board by applying game rules and algorithmic checks. Understand counting moves, verifying winning conditions, and ensuring legal play sequences. This lesson helps you develop problem-solving skills essential for coding interviews involving game state validation.

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Statement

Given a tic-tac-toe board as an array of strings. Return true if and only if it is possible to reach this board state during the course of a valid tic-tac-toe game.

The board is a 3 x 3 array that consists of characters space ( ), X, and O where the space character represents an empty square.

Following are the rules of the game:

  • Players take turns putting their characters in the blank squares ( ).
  • The first player always places the X characters, while the second player always places the O characters.
  • When either X or O occupies three consecutive places in any row, column, or diagonal, that player wins, and the game is over.
  • The game also ends if all squares are non-empty.
  • If the game is over, neither player can take any more moves.

Examples

Example 1

The following board is an example of a valid tic-tac-toe board:

Sample input

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