string_manipulation_swift

import Foundation

func remove(input: String, first: Int, last: Int) -> String {
    // we require a variable to manipulate strings
    let newString = input
    // modify newString and return the result

    let firstIndex = newString.index(newString.startIndex, offsetBy: first)
    let lastIndex = newString.index(newString.endIndex, offsetBy: (last * -1))

    let firstSubstring = newString[..<firstIndex]
    let lastSubstring = newString[lastIndex..<newString.endIndex]

    return String(firstSubstring + lastSubstring)
}

func remove(input: String, first: Int, last: Int) -> String {
    // we require a variable to manipulate strings
    var newString = input
    // modify newString and return the result

    if first + last > newString.count {
        return ""
    }

    var counter = first
    var firstSubstring = ""
    while counter > 0 {
        firstSubstring += String(newString.removeFirst())
        counter -= 1
    }

    counter = last
    var lastSubstring = ""
    while counter > 0 {
        lastSubstring += String(newString.removeLast())
        counter -= 1
    }

    return String(firstSubstring + lastSubstring.reversed())
}

print(remove(input: "Hello there world!", first: 5, last: 7))