Solution: Valid Sudoku
Understand how to determine if a Sudoku board configuration is valid by using hash maps to track digits in each row, column, and 3x3 sub-box. This lesson helps you implement a single-pass solution that efficiently enforces Sudoku rules and ensures no digit duplicates across these constraints, without solving the board itself.
We'll cover the following...
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...