most sudokus ..
.. are created by computers. Afterwards the computers solve them by using the same set of techniques that a human would probably do (i.e. not the simple-to-code brute force approach that a computer programmer would usually choose for a task such as this). The number of steps to solve, and the types of techniques, are used to rate its difficulty. As far this is how I've heard it works.
Anyway, writing a computer program to solve a sudoku is an easy task. The really nice thing about the app in the video was how it found the sudoku on the photo, and how it recognized the numbers. Also seems like a nice UI.
(, Sun 8 Mar 2009, 14:01, Reply)
I was amazed when it worked
I am still a bit surprised that it works so well.
Normally when you start using any image processing algorithms you find that they don't quite work as well as you were lead to believe by the pretty pictures in the research papers.
Even though I must have run it hundreds of times doing testing. It still puts a smile on my face.
(, Mon 9 Mar 2009, 16:00, Reply)