gistfile1.txt

extension Character {
    var asciiValue: UInt32? {
        return String(self).unicodeScalars.filter{$0.isASCII}.first?.value
    }
}

func sort(str: String, isReversed: Bool) -> String {
    if (isReversed) {
        return String(str.characters.sorted(by: compareCharactersReversed))
    }
    else {
        return String(str.characters.sorted(by: compareCharacters))
    }
}

func compareCharactersReversed(c1: Character, c2: Character) -> Bool {
    return !compareCharacters(c1: c1, c2: c2)
}

func compareCharacters(c1: Character, c2: Character) -> Bool {
    var n1:Double = Double(c1.asciiValue!)
    var n2:Double = Double(c2.asciiValue!)
    let a:Double = Double(Character("a").asciiValue!)
    let z:Double = Double(Character("z").asciiValue!)
    let A:Double = Double(Character("A").asciiValue!)
    
    let diffaA = a - A
    
    if (n1 >= a && n1 <= z) {
        n1 = n1 - diffaA - 0.5
    }
    if (n2 >= a && n2 <= z) {
        n2 = n2 - diffaA - 0.5
    }
    
    return n1 < n2
}

sort(str: "324392784", isReversed: false)

sort(str: "324azbcAU", isReversed: true)