Solution: Valid Sudoku
Explore how to verify the validity of a 9x9 Sudoku board by checking for duplicate digits in rows, columns, and 3x3 sub-boxes. This lesson teaches you to implement an efficient, single-pass hash map solution in C# that avoids complex backtracking, focusing instead on constraint checking for coding interviews.
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Statement
Given a 9 × 9 Sudoku board, determine whether it is valid. A board is considered valid if all of the following conditions hold (considering only the filled cells):
Each row contains the digits
1–9at most once.Each column contains the digits
1–9at most once.Each of the nine 3 × 3 sub-boxes contains the digits
1–9at most once.
You do not need to check whether the Sudoku is solvable; only whether the current filled entries obey these rules.
Note: A partially filled Sudoku board can be valid even if it is not necessarily solvable. You only need to verify that the filled cells adhere to the given rules.
Constraints:
board.lengthboard[i].length...