Enigma 329: Clear short circuit
22 January 2016
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From New Scientist #1477, 10th October 1985 [link]
An n-circuit 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 length of a circuit is just the sum of the lengths of the legs. Thus A has length 7, and B has length 11.
Can you find a clear 12-circuit with a length of 21 (or less)?
A similar problem to Enigma 325.