Sudoku Solver using Constraint Satisfaction Problem

Sudoku is a logic-based, combinatorial number-placement puzzle.

Objective of the game is to fill a 9x9 grid with digits based on the following constraints:

- Each Row should contain all digits from 1 to 9
- Each Column should contain all digits from 1 to 9
- Each of 3x3 subgrid should contain all digits from 1 to 9