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Triple Negative (Posted on 2004-02-12) Difficulty: 4 of 5
Using only two inverters and an unlimited number of AND and OR gates in a logic circuit, show how to invert an arbitrary number of inputs.

(For instance, if you have four inputs, the circuit will have four outputs that are the inverses of the four inputs)

No Solution Yet Submitted by DJ    
Rating: 4.1250 (8 votes)

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Solution So... | Comment 14 of 19 |
(In reply to Of course you could do this by Charlie)

I don't think you actually can invert an arbitrary number of inputs with just 2 inverters. I think the original quote from the internet is correct: with n inverters you can do 2^n - 1 inversions. Put another way, to do i inversions, you need n = ceil(log(i+1)) inverters, using base-2 logarithms.
  Posted by Charlie on 2004-02-14 11:19:13

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