What is a fast way to convert a string of two characters to an array of booleans?

Question

I have a long string (sometimes over 1000 characters) that I want to convert to an array of boolean values. And it needs to do this many times, very quickly.

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Answer 1

I need to some testing to be sure but I think one issue with many approaches given including the original map is that they need to iterate over the string to count the characters and then a second time to actually process the characters.

Have you tried:

let output = [Bool](input.characters.lazy.map { $0 == "1" })

This might only do a single iteration.

The other thing that could speed things up is if you can avoid using strings but instead use arrays of characters of an appropriate encoding (particularly if is more fixed size units (e.g. UTF16 or ASCII). Then then length lookup will be O(1) rather than O(n) and the iteration may be faster too

BTW always test performance with the optimiser enabled and never in the Playground because the performance characteristics are completely different, sometimes by a factor of 100.