Translate a column index into an Excel Column Name

Question

Given a columns\' index, how can you get an Excel column name?

The problem is trickier than it sounds because it\'s not just base-26. The columns

Answer 1

this is with Swift 4 :

@IBAction func printlaction(_ sender: Any) {
    let textN : Int = Int (number_textfield.text!)!
    reslut.text = String (printEXCL_Letter(index: textN))
}


func printEXCL_Letter(index : Int) -> String {

    let letters = ["a", "b", "c","d", "e", "f","g", "h", "i","j", "k", "l","m", "n", "o","p", "q", "r","s", "t", "u","v","w" ,"x", "y","z"]

    var index = index;
    index -= 1
    let index_div = index / 26

    if (index_div > 0){
        return printEXCL_Letter(index: index_div) + letters[index % 26];
    }
    else {
        return letters[index % 26]
    }
}