Column Validation – Checks that each column contains distinct numbers and does not exceed the allowed range. 3x3 Subgrid Validation – Confirms that each 3x3 section does not contain repeated numbers.

This Java program solves a 9x9 Sudoku puzzle using a backtracking algorithm. It fills the grid so that each row, column, and 3x3 subgrid contains the digits 1 to 9 exactly once. Starting with a ...