TrelloInterviewProblem.swift

/**

 Solution to an interview question posted by trello. I came across the link
 not actually looking for a job but I love puzzles. So I went ahead and solved
 it :)

 Decrypts a value hashed by the following Pseudo code:

    Int64 hash (String s) {
        Int64 h = 7
        String letters = "acdegilmnoprstuw"
        for(Int32 i = 0; i < s.length; i++) {
            h = (h * 37 + letters.indexOf(s[i]))
        }
        return h
    }
 
 - Parameter h: The hashed result to decode.
 
 - returns: The original string used to create the hash.
 
 */
func decrypt(var h: Int) -> String {
    let letters = "acdegilmnoprstuw"
    var result = ""
    while h > 7 {
        let index = h % 37
        result += String(letters[letters.startIndex.advancedBy(index)])
        h = (h - index) / 37
    }
    return String(result.characters.reverse())
}

// decrypt(680131659347) -> "leepadg"
// decrypt(25377615533200) -> "nsanswer"