Solving LeetCode's 37. Sudoku Solver Problem (Hard): A Step-by-Step Guide
Introduction
Welcome to our LeetCode substack! In this post, we'll be walking through the process of solving the Sudoku Solver problem using Python. This problem asks us to fill in the empty cells of a Sudoku puzzle, satisfying all of the Sudoku rules.
Problem Statement
Given a 9x9 Sudoku puzzle board, we need to fill in the empty cells with digits 1-9 in such a way that each row, column, and 3x3 sub-box contains exactly one occurrence of each digit.
Solution
To solve this problem, we can use a recursive backtracking approach. We start by iterating over each cell in the board.
If the cell is empty, we try each digit from 1 to 9 in that cell.
For each digit, we check if it satisfies the Sudoku rules for that row, column, and sub-box. If it does, we fill in the cell with that digit and recursively call the solver function on the next cell.
If the recursive call returns True, we know that we have found a valid solution and can return True.
If the recursive call returns False, we backtrack by resetting the current cell to empty and trying the next digit.
Here's the Python code to implement this solution:
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