Validate a 9×9 grid under constraints

Q: Validate a 9×9 grid under constraints

This question evaluates the ability to perform constraint validation on a fixed-size 9×9 grid, testing skills in matrix/array handling, duplicate detection and use of simple data structures for correctness checking.

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Question

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Problem

You are given a 9×9 grid representing a partially filled puzzle. Each cell contains either:

a digit character '1' – '9' , or
the character '.' meaning empty.

Determine whether the current filled cells are valid under these rules:

No digit '1' – '9' repeats within any row.
No digit repeats within any column.
No digit repeats within any of the nine 3×3 sub-grids.

Return true if the filled cells satisfy all rules; otherwise return false.

Input / Output

Input: board — a 9×9 array of characters
Output: boolean

Notes / Constraints

You only need to validate the currently filled cells; you do not need to solve the puzzle.
The board is always 9×9.

Example

If a row contains two '5' values (ignoring '.'), the board is invalid and you should return false.

Validate a 9×9 grid under constraints

Quick Overview

Problem

Input / Output

Notes / Constraints

Example

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