Enigma 325: Clear thin circuit
25 December 2015
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From New Scientist #1473, 12th September 1985 [link]
An n-circuit is drawn on a triangular grid made up of equilateral triangles. It is a closed path of n different points and n different legs. Every leg runs along a grid-line and every point is a junction of grid-lines. Legs do not overlap, but they may cross.
A clear circuit is one that you cannot make a circuit with just some of the points. Thus the 5-circuit A is not clear. Points 1, 2 and 5 would make a 3-circuit: so would points 3, 4 and 5. But B is clear.
The fatness of a circuit is the area it encloses. Thus A has fatness 5 (measured by the number of little triangles enclosed), and B has fatness 7.
Can you find a clear 9-circuit with a fatness of 9 (or less)?
Happy Christmas from Enigmatic Code!