A basic sudoku solver based on a backtracking algorithm
Resources used during the creation of this solution: https://en.wikipedia.org/wiki/Sudoku_solving_algorithms http://pi.math.cornell.edu/~mec/Summer2009/meerkamp/Site/Solving_any_Sudoku_I.html
It is a brute force solution, which means that it will try all combinations until it finds a solution.
The issue with this is that there are certian sudoku puzzles that it will spend a significant amount of time trying to solve.
A example of this can be found in the test: SolveSudokuPuzzle_HardSudokuProblem_ForBacktracking_SolveSolution.
In this test the solution for the top row is 987654321, but the puzzle provides no values for the top row. Which in turn means that the algorithm will spend a significant amount of time trying to work its way up to 987654321.
More info about the weakness with backtracking can be found here