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  • Python – Solving 7 Queen Problem with Tabu Search – Useful code

    Python – Solving 7 Queen Problem with Tabu Search – Useful code


    The n-queens problem is a classic puzzle that involves placing n chess queens on an n × n chessboard in such a way that no two queens threaten each other. In other words,
    no two queens should share the same row, column, or diagonal. This is a constraintsatisfaction problem (CSP) that does not define an explicit objective function. Let’s
    suppose we are attempting to solve a 7-queens problem using tabu search. In this problem, the number of collisions in the initial random configuration shown in figure 6.8a is 4: {Q1– Q2}, {Q2– Q6}, {Q4– Q5}, and {Q6– Q7}.

    The above is part of the book Optimization Algorithms by Alaa Khamis, which I have used as a stepstone, in order to make a YT video, explaining the core of the tabu search with the algorithm. The solution of the n-queens problem is actually interesting, as its idea is to swap queen’s columns until these are allowed to be swaped and until the constrains are solved. The “tabu tenure” is just a type of record, that does not allow a certain change to be carried for a number of moves after it has been carried out. E.g., once you replace the columns of 2 queens, you are not allowed to do the same for the next 3 moves. This allows you to avoid loops.

    https://www.youtube.com/watch?v=m7uAw3cNMAM

    Github code:

    Thank you and have a nice day! 🙂



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  • VBA – A* Search Algorithm with Excel – Useful code


    Ok, so some 10 years ago, I was having fun coding A* Search Algorithms in Excel in VitoshAcademy and this is what I had built back then:

    VBA – A* search algorithm with Excel – Really?

    VBA – A Search Algorithm with VBA – Teil Zwei

    The second one is actually quite fun and I had forgotten about it. Today, I will present a third one, that has a few more features, namely the following:

    • It can be copied completely into a blank Excel’s VBA module, without any additional setup and it will work
    • You can choose for distance method (Manhattan or Heuristics)
    • You can choose for displaying or not calculations in Excel (
      writeScores = False )
    • You can
      ResetAndKeep() , which cleans out the maze, but keeps the obstacles
    • You can setup your own start and goal cell. By simply writing
      s and
      g , somewhere in the PLAYGROUND.
    • You can change the speed of writing in the Excel file, by changing the
      delay variable.

    These are the current commands:



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