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🔥Valid Sudoku: 9x9 Bitmask / Hash ValidationMedium
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MediumArrays & Hashing•Acceptance: 59.2%

Valid Sudoku: 9x9 Bitmask / Hash Validation

Targeted in FAANG & Tech OA:AmazonMicrosoftUber
Real-World Engineering Context
Used in constraint satisfaction solvers (SMT solvers, Z3), puzzle verification engines, and bitmask matrix validations.
Determine if a `9 x 9` Sudoku board is valid. Only the filled cells need to be validated according to the following rules: 1. Each row must contain the digits `1-9` without repetition. 2. Each column must contain the digits `1-9` without repetition. 3. Each of the nine `3 x 3` sub-boxes of the grid must contain the digits `1-9` without repetition. Note: A Sudoku board (partially filled) could be valid but is not necessarily solvable. Only the filled cells need to be validated.

Sample Test Cases

Input: [[["5","3",".",".","7",".",".",".","."],["6",".",".","1","9","5",".",".","."],[".","9","8",".",".",".",".","6","."],["8",".",".",".","6",".",".",".","3"],["4",".",".","8",".","3",".",".","1"],["7",".",".",".","2",".",".",".","6"],[".","6",".",".",".",".","2","8","."],[".",".",".","4","1","9",".",".","5"],[".",".",".",".","8",".",".","7","9"]]]
Expected: true
Input: [[["8","3",".",".","7",".",".",".","."],["6",".",".","1","9","5",".",".","."],[".","9","8",".",".",".",".","6","."],["8",".",".",".","6",".",".",".","3"],["4",".",".","8",".","3",".",".","1"],["7",".",".",".","2",".",".",".","6"],[".","6",".",".",".",".","2","8","."],[".",".",".","4","1","9",".",".","5"],[".",".",".",".","8",".",".","7","9"]]]
Expected: false

Constraints

  • board.length == 9
  • board[i].length == 9
  • board[i][j] is a digit '1'-'9' or '.'.
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