As you know, this series is dedicated to those individuals whose work makes me feel insignificant, and my existence, meaningless.

I love Sudoku.  If I was to put these puzzles into easy, medium, hard, and expert categories, I can deal up to hard level, comfortably.  Now the question is, what makes a hard puzzle, hard.  You may think that it is the number of count of pre-solved numbers make it so.  Unfortunately, I have seen cases where a hard puzzle had more initial numbers than a medium one.  I also wrote a program to solve the Sudoku puzzle using some brute force, by generating all possible combinations of the solution based upon the initial hints provided.  In this method it did not matter to the program, whether the puzzle was easy, medium, or hard etc.

So, once again, what makes a puzzle hard to us.  Apparently this team of students from the University of Washington wrote this paper on the mathematics of Sudoku.  Almost none of it makes sense to me, a mathematically challenged person, yet it makes me feel to go back and hide in my little shell.

So, kudos to the Team2280 from the University of Washington for explaining the math behind the Sudoku puzzles.