Exploring different approaches to solving Sudoku puzzles.

An example of a backtracking approach to solving a difficult Sudoku. This is an example of depth-first search (DFS). Here you can see the algorithm explores all possible solutions, recursing through empty cells, trying values and using backtracking when needed. Although not the fastest solution, this approach is so exhaustive it will eventually get there!

The gif shows the cells that have been tried but have no solution yet in a light orange and the cells that are in the current possible solution in light blue. The Sudoku can get to almost the end of the puzzle and look like it is about to be solved, only to go back to the beginning!