Wednesday, April 25, 2007

Summer 2007: Nurikabe

The idea of Nurikabe is to color each square in an n x n grid white or black according to the following rules:
  • Each numbered cell must be part of a connected white region (connected always means edge-to-edge, not corner-to-corner).
  • Each connected white region must contain exactly one number, and this value is the number of white cells in the region (including the numbered cell).
  • The black region must be connected.
  • There can be no 2 x 2 blocks of black cells.
Below is a 5 x 5 game and its solution.

This month's puzzle is to solve the following 9 x 9 Nurikabe puzzle.