Hosted by The Math Forum## Problem of the Week 1077## Nurikabe
The March 21 I found nurikabe (also known as Islands in the Stream), invented by Nikoli, to be particularly pleasing. This diagram gives a simple nurikabe, along with its solution:
The idea is to color each square black or white, subject to the following rules, where "connected" always means in a horizontal or vertical direction, not diagonal. - Each numbered square will be white.
- Every connected white region contains exactly one of the given numbers, and the number of squares in the region equals the number it contains.
- The set of all black squares is connected.
- The set of all black squares does not contain a 2×2 set of black squares.
So in this 9×10 nurikabe -- Problem 1077 -- one knows immediately that the three squares connected to the "1" are black.
Source: Wikipedia. © Copyright 2007 Stan Wagon. Reproduced with permission. |

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26 March 2007