Solving Sudoku puzzles with Python To those of you unfamilar with a Sudoku puzzle, they are a logic puzzle that has recently (2. UK and US, appearing in most newspapers alongside the crosswords and other diversions. Congratulations to Carol Vorderman of . Other (mis)spellings include So Duko, Soduko and Suduko. There are more tactics pages available of course, for example by Simon Armstrong and Angus Johnson. Programming Sudoku is a challenge for computer programmers. The program found in the book Programming Sudoku is basic. What are the most efficient programming algorithms to solve sudoku puzzles? Is there any C program to solve sudoku puzzles? What are the ways to write a program which solves Snake Cube Puzzle? An Integer Programming Model for the Sudoku Problem. Solution 1 Write a computer program to execute the logic that a person uses to solve a Sudoku puzzle. How to Solve a Sudoku. Sudoku is a numbers puzzle that has swept the world. It is very fun to play. You can recreate the puzzle on bigger paper to help with this. Write all the numbers that don't appear in that row. Motivation Anyway, after reading Solving Sudoku in the Autumn 2. Warwick the Magazine (catchy title!) by Psychology lecturer Dr Neil Stewart, I finally got round to trying to solve Sudoku with Python. Test cases Of course, any good programmer should test their handy work. So, where can we find lots of (hard) Sudoku puzzles to test with? It turns out there is an active group on this web forum and they have compiled a whole bunch of test puzzles (hosted here) including: These are simple text files, with one line of 8. They use a full stop (period) for an unknown entry. How to represent Sudoku Puzzles in Python Most . In each empty grid square (or cell), they write down all nine digits (very small!) and then cross out those which are not allowed due to existing solved squares. If you are using a recent version of Python it might be more efficient to use a set object instead of a list.. Solving - Step One - Trivially easy When any cell is solved, then that number can be removed from the candidate lists for all the other cells in the same row, column or 3x. Solving - Step Two - Easy Each digit must appear once (and only once) in each of the nine rows, nine columns, nine 3x. Solving - Step Three - Medium - Slicing & Dicing You don't actually need this (a few levels of supposition will do, its just a bit slow). Anyway, this works by considering each of the nine numbers in each of the nine 3x. If all the candidates fall into a single row (or column) then that number can be removed from the other two rows (or columns). See method overlapping. Simon Armstrong calls this . Solving - Step Four - Hard - Supposition and Contradiction Just doing the above simple logical steps above turns out to be enough to solve most . In fact, most newspapers etc seem to grade their puzzles using computer programs - if this is enough then its an easy puzzle. You might still need a very good memory or a pencil. What I choose for my program is akin to proof by contradiction. We pick an unsolved cell, and chose one of the possible candidate values. Then apply the above rules, and see if this leads to an error (contradiction). Sudoku solving algorithms This article has multiple. Players may use a wide range of strategies to solve Sudoku puzzles. The constraint program modeling and solving Sudoku will in most solvers have less than 100 lines. Step by step to crack Programming Interview questions 30: Solve a sudoku Solution (recursive way) 1. Programming Interview 30: Write a Sudoku solver ProgrammingInterview. Subscribe Subscribed Unsubscribe 9,655 9K. The popular Japanese puzzle game Sudoku is based on the logical placement of numbers. An online game of logic, Sudoku doesn’t require any calculation nor special math skills; all that is needed are brains and concentration. SUDOKU PLACE ARTICLES > WRITING SUDOKU: How To Write Sudoku. Solve Sudoku (Without even thinking!). If so, then the original suposition (or guess) was false, and that value can be removed from the candiate list for the cell. Despite it being completely logical, some people consider it to be . Adding that code also made the program four times faster. Download My Python Sudoku solver is available to download: Note that my code has no graphical user interface (GUI) - its purely text based. If you are looking for something like that, then there are lots more python Sudoku solvers out there (e. Shed Skin (Python to C++) Mark Dufour used an early version of my code as a test case (. He said its use of lists- of- lists- of- lists- of- integers gave its type inference code a good workout! You can download his tool from the Shed Skin sourceforge page, or read more on the blog.
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