swift - Find nearest smaller number in array

Question

I would like to be able to find the nearest smaller value in an array of numbers. For instance, if I have:

[1, 4, 6, 9, 14, 39]

And I'm looking for the nearest value smaller than:

8

The function would return:

6

Additionally, if I pass a number greater than the maximum value in the array, it should return the maximum. If I pass a number smaller than the minimum, it should return nil.

I tried doing this using the first function on arrays, however this on its own doesn't produce the result I'm looking for as I would need something like this:

numbers.first(where: { $0 <= target && $1 < target })

but unfortunately, this isn't valid. Any suggestions? I know this could be done fairly trivially with a while loop, however I was hoping there would be a cleaner, functional way.

Answer 1

Given that the array is sorted , You need

if let value = numbers.last(where: { $0 <= target }) {
  print(value)
}