# Killer Sudoku

If the milk delivery problem looks familiar to newspaper readers, then perhaps it really is. *Killer Sudoku* is an advanced version of the popular *Sudoku* puzzle. In *Killer* *Sudoku*, as in *Sudoku*, the player is asked to place the numbers one to nine in a grid with each number occurring once and once in each row and column. However, rather than giving the player some starting numbers as in *Sudoku*,* Killer Sudoku* tells how the numbers add up in certain combinations. This is precisely the same as the milk delivery problem.

A very similar puzzle is called *Griddler*, where the player is given a square grid and told how many black squares there are in each row and column, along with some extra information about how they are grouped. Solving a *Griddler* problem is another exercise in tomography. Usually we solve *Sudoku* and *Griddler* problems in the newspapers by using a pencil, eraser, and a bit of luckand judgment. However we will describe a computer algorithm to solve even more general problems.

Check out these links:

http://www.killersudokuonline.com/

http://www.sudoku.org.uk/killersudoku.asp

http://www.griddler.co.uk/