FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in          Games  Calendar Log in to check your private messages    Translating rownr/colnr to boxnr/cellnr within box          Sudoku Programmers Forum Index -> Programming sudoku View previous topic :: View next topic   Author Message evert Joined: 30 Aug 2005 Posts: 68 : Location: Amsterdam Items Posted: Mon Nov 28, 2005 10:57 pm    Post subject: Translating rownr/colnr to boxnr/cellnr within box I just found out that the function that translates rownrs/colnrs into boxnrs/cellnrs inverts itself: Code: function Trfi(i, j : integer) : integer; begin   result := (((i - 1) div 3) * 3) + ((j - 1) div 3) + 1; end; function Trfj(i, j : integer) : integer; begin   result := (((i - 1) mod 3) * 3) + ((j - 1) mod 3) + 1; end; //  boxnr   := Trfi(rownr,colnr); //  bcellnr := Trfj(rownr,colnr); //  rownr   := Trfi(boxnr,bcellnr); //  colnr   := Trfj(boxnr,bcellnr); Back to top xyzzy Joined: 24 Aug 2005 Posts: 80 : Items Posted: Tue Nov 29, 2005 1:59 am    Post subject: Of course it's faster to use a lookup-table. Integer division and modulus by non-powers of two are the slowest operations on modern CPUs. It's still interesting that you can use the same lookup tables for both directions. Back to top Display posts from previous: All Posts1 Day7 Days2 Weeks1 Month3 Months6 Months1 Year Oldest FirstNewest First         Sudoku Programmers Forum Index -> Programming sudoku All times are GMT Page 1 of 1   Jump to: Select a forum Sudoku----------------Solving sudokuSetting sudokuProgramming sudokuThe mathematics of sudokuExotic sudoku Library----------------PuzzlesSoftwareSudoku elsewhere Not sudoku----------------Random thoughtsForum feedback  You cannot post new topics in this forum You cannot reply to topics in this forum You cannot edit your posts in this forum You cannot delete your posts in this forum You cannot vote in polls in this forum   Powered by phpBB © 2001, 2005 phpBB Group Igloo Theme Version 1.0 :: Created By: Andrew Charron