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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 according to the mentioned rules.
Input: board = [["5","3",".",".","7",".",".",".","."],[...]]
Output: true
Topics: arrays, hash-map
Asked by: Google, Amazon, Meta, Microsoft
Time complexity: O(1) - constant grid operations. Space complexity: O(1) - constant space limit.