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Problem of the Week 919

A Planar Crossing

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You have available the three basic logic gates: AND, OR, and NOT gates. The goal is to build a circuit that allows two signals to cross. The constraint is that the circuit has to be "planar", that is you can't cross signals (otherwise it would be trivial).

Put graphically:

Source: John Guilford (Agilent Technologies)

© Copyright 2000 Stan Wagon. Reproduced with permission.

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