Further tweaking of the algorithms sped up the program further.Sudoku is one of the most popular puzzles on the planet. This increased the generation speed tremendously. The same program used to solve puzzles can also be used to randomly generate puzzles.Īt this point, the Python program was getting a bit slow, especially when generating more difficult puzzles. This is a more complex approach, but is faster. I wrote the program simulating how a person would solve the puzzle, applying various analytical techniques until a solution was reached. All possibilities are tried, and when an impasse is reached, guesses are backed out, and the next possibility is tried.įor my program, I took the analytical approach. The obvious one is the brute-force back-tracking method. There are a couple of approaches to solving Sudoku puzzles programmatically. I wrote my first program in Python, which is an excellent language for rapid development. Right away, I could see that the puzzle was quite amenable to being solved by computer program. When I first saw a Sudoku puzzle on the pages of the Toronto Star, of course, I had to try it out. The latter puzzles of this group have just 14 initial values. The other puzzles are more Nonomino puzzles, but with 21 or fewer initial values.

The first group of puzzles have just 20 initial values. In this game, the two diagonals must also have the digits from 1 to 9 represented just once.įinally, the Challenge Puzzles provide some miscellaneous challenging puzzles. The Diagonal Sudoku Puzzles offer yet another challenging variation on the puzzle. Use of an advanced technique may or may not be required for these puzzles. Instead of nine 3×3 regions, the puzzle is tiled with irregularly shaped nonominos.

If you want something a little bit different, the Nonomino Puzzles provide a twist to the game. Are they any easier or more difficult than the others? Try them and find out! The last section of normal Sudoku puzzles are the Blackjack Puzzles, so named because they all have only 21 seed values. The Advanced puzzles may be some of the hardest Sudoku puzzles you’ll find on the internet. In the Hard Puzzles and Advanced Puzzles, use of the advanced techniques is definitely needed to solve the puzzles. However, some of the advanced techniques may help you out with those puzzles. For both the Beginner and Standard puzzles, you don’t need to use any of the “advanced” solving techniques. Once these get too easy for you, you can move up to the Standard Puzzles, which have fewer seed values. These all have 30 seed values and 2-fold rotation symmetry. If you are new to Sudoku, you may want to start with the Beginner Puzzles. Here, you can find all the Sudoku puzzles you could ever want, all in printable form. The first volume of “Advanced” puzzles includes almost all of the puzzles previously posted to my blog. Check the index at the top for my collections of puzzles, 20,000 per page. And most of my comments had nothing to do with Sudoku anyways, and really belonged elsewhere on my blog.Īnd so I decided to present the puzzles in a slightly different format, within the permanent pages of my web site. After about 50 postings, I started running out of things to say. Unfortunately, after a while, that got to be a bit unwieldy. The following represents the solution to this puzzle:Īt first, I offered some of my puzzles on my blog.

Free printable diagonal sudoku puzzles