Validate a Partially Filled Sudoku Board

Implement a function isValidSudoku(board) that takes a partially completed $$9 \times 9$$ Sudoku grid and returns true if the currently filled cells obey the standard Sudoku uniqueness rules, and false otherwise. The grid is given as a list of nine strings. Each string has length 9. A character is either '.' (empty) or a digit from '1' to '9'. You only need to check the digits that are already present; you do not need to determine whether the board can be completed or…