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 lo

Answer 1

Given that the array is sorted , You need

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

Answer 2

This is a generic solution using binary search. The array must be sorted

extension RandomAccessCollection where Element : Comparable {
    func lowerElement(of value: Element) -> Element? {
        var slice : SubSequence = self[...]

        while !slice.isEmpty {
            let middle = slice.index(slice.startIndex, offsetBy: slice.count / 2)
            if value < slice[middle] {
                slice = slice[..<middle]
            } else {
                slice = slice[index(after: middle)...]
            }
        }
        return slice.startIndex == self.startIndex ? nil : self[self.index(before: slice.startIndex)]
    }
}

let array = [1, 4, 6, 9, 14, 39]
let result = array.lowerElement(of: 8)
print(result)