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

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.

let input: String = "001"

let output: [Bool] = [false, false, true]

My naive attempt was this:

input.characters.map { $0 == "1" }

But this is a lot slower than I'd like. My profiling has shown me that the map is where the slowdown is, but I'm not sure how much simpler I can make that.

I feel like this would be wicked fast without Swift's/ObjC's overhead. In C, I think this is a simple for loop where a byte of memory is compared to a constant, but I'm not sure what the functions or syntax is that I should be looking at.

Is there a way to do this much faster?

UPDATE:

I also tried a

output = []
for char in input.characters {

    output.append(char == "1")
}

And it's about 15% faster. I'm hoping for a lot more than that.

Answer

This is faster:

// Algorithm 'A'
let input = "0101010110010101010"

var output = Array(count: input.characters.count, repeatedValue: false)
for (index, char) in input.characters.enumerate() where char == "1" {
    output[index] = true
}

Update: under input = "010101011010101001000100000011010101010101010101"

0.0741 / 0.0087, where this approach is faster that author's in 8.46 times. With bigger data correlation more positive.

Also, with using nulTerminatedUTF8 speed a little increased, but not always speed higher than algorithm A:

// Algorithm 'B'
let input = "10101010101011111110101000010100101001010101"
var output = Array(count: input.nulTerminatedUTF8.count, repeatedValue: false)
for (index, code) in input.nulTerminatedUTF8.enumerate() where code == 49 {
    output[index] = true
}

In result graph appears, with input length 2196, where first and last 0..1, A – second, B – third point.
A: 0.311sec, B: 0.304sec