**Problem: **Given a filled sudoku, write a program to check if sudoku is valid or following all of its rules.

**SUDOKU rules: **

- Each column contains all of the digits from 1 to 9 only once.
- Each row contains all of the digits from 1 to 9 only once.
- Each of the nine 3×3 sub-grid contains all of the digits from 1 to 9 only once.

**Approach:**

If we go by the rules of sudoku, we need a function for each rule (row, column and 3×3 matrix). Each function will validate whether all numbers from 1 to 9 are present and there are no duplicates present. There are 9 rows, 9 columns and 9 3×3 matrix, we will validate each of those.

See the code below for more understanding.

**Complete Code:**

**Output:**

Given SUDOKU is valid