This one's simple: simply choose the most constrained variable first - that is, the cell with the least options. There are other strategies you might want to try implementing, although you will get diminishing returns. This is known as the 'naked pairs' strategy. When two cells in a unit have been reduced to the exact same pair of possible values, you can rule those values out for all other cells in the same unit. When the value of a cell has been deduced, you can remove that value from all other cells in the same unit (row, column, or box). Here are a couple of inference procedures you might apply: You can make full use of a procedure by repeatedly applying it until it produces no change. If you reach a state in which all of the values of a variable have been ruled out, you know the sudoku is not solvable from that state, so you backtrack.Īn inference procedure looks at the present search state, and uses knowledge of the constraints to eliminate possible assignments. The improved algorithm would be a backtracking search, like the one you already have, but at each node of the search tree you apply constraint propagation to immediately rule out some of the options. This will lead to something like this: A1 - ), which would allow you to incrementally rule out values. Naively: A Cell C can have only values which are not available in its row, its column and its box. There is a much more efficient way to do this: find the cell which has only one Value, and fill that first, this will lead you to fill in first few digits of board pretty quickly, and constrain your solution space.įor this: Just iterate over every cell, and store it in dict what are possible values this cell can have. So, the first thing I noticed about your program is that you implement a simple way to select which cell to fill: Find the first empty one, and try filling that. However, if you need more explicit help or I am not clear enough, leave a comment, and I would provide more details as needed. I am going to provide a much more over-the-top strategies to deal with Sudoku rather than outright code snippets so you can try it out on your own. I am trying to succeed in passing a coding challenge in a competitive platform, which my specific code times out. Tests: 100 random tests and 5 assertions per test It might require some sort of brute force. In the case of the multiple solution sodoku. The solution only needs to give one valid solution The Sudokus tested against your function will be "insane" and can have Will take one argument consisting of the 2D puzzle array, with the Write a function that will solve a 9x9 Sudoku puzzle. However, it is rather slow for hard Sudokus like this: , Once you are finished with your entries, you can click on the “Check Solution” button to see the results if you have entered the correct entries or not.This is my naive approach on implementing a Sudoku solver, which is okay for simple Sudokus like this: puzzle = ,.Eraser tool can be used to clear an entry you made.You can choose from the numbers to fill in the blanks.You will see the display with numbers from 1 through 9. Open the control panel by checking the “Show controls to play online” option.There is also an option of playing Sudoku online. To see the solution online, click on the “Show solution” button.įor the printed version, the solution will be included at the end of the generated PDF file. You can generate as many as Sudoku puzzles as you want with this Sudoku Generator. Simply download, print and start playing. You can play this Sudoku with pencil and paper. 9×9 is a grid with difficult puzzles and 4×4 is an easy game perfect for beginners. There are two levels that you can choose to play. Similarly, for 4×4 grid, you will need to fill empty spaces in such a way that every row, column and every 2×2 box contains the numbers from 1 to 4.ĭepending on the difficulty level you choose, it can be a fun and interactive game for everyone. If you select 9×9 grid, you will fill empty spaces in such a manner that every row and column as well as every 3×3 box contains the numbers from 1 to 9. In order to play this interactive game, you need to fill in the empty spaces of a 9×9 or 4×4 grid. Sharpen your mind and improve concentration skills with Sudoku.
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