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A Neat Bitwise Trick for Swapping Even and Odd Bits

https://www.dailycodingproblem.com/blog/neat-bitwise-trick/

by lawrencewu • 8 years ago

1 3 8 years ago

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dailycodingproblem.com

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joezydeco2• 8 years ago

8 bit input? Use a pre-generated lookup table. Store it in ROM.

The table deference will take 1 or 2 operations instead of the AND/SHIFT/PUSH/AND/SHIFT/POP/OR described in the answer.

lawrencewu• 8 years ago

You're right, 8 bits is small enough to just store in a table.

This trick will work for any number of bits though. You might not want to use 2^64 entries in your table.

joezydeco2• 8 years ago

The question was an unsigned 8-bit input, not an arbitrary number.

And the "trick" given in the answer still depends on a fixed number of input bits, no matter if it's 8, 32, or 10^100.

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