This function takes in a 2D array and determines if it is a valid Sudoku board. A Sudoku board is valid if each row, column, and 3x3 subarray contains exactly 9 integers.

A.I. Evaluation of the Solution

The candidate's solution correctly solves the problem. The solution is complete, with functions to check rows, columns, and 3x3 subarrays. The candidate's approach is clear and easy to follow.