playground_compress

let input = "AAABBACCiurioweurowiquroqwiuroiweurljklsdkldskllksdklasdklkkkddkddddddsd--000"
            

var numberLetter = Int(input.count)

var compress:String =  ""

var lastLetter:String = ""

var totalLetter:Int = 0

func concatString(_ compress:String , _ wordConcat:String, _ countString:Int)->String {
    if(totalLetter == 1) {
        return compress + wordConcat
    }
    else {
         return compress + lastLetter + String(countString)
    }
   
    
}
for  i in 0..<numberLetter {
    let index = input.index(input.startIndex,offsetBy:i)
   
    let currentword:String = String(input[index])
    //Fist time in loop it`s necessary set lastword equals current word
    if(i == 0){
        lastLetter = currentword
    }
    
    //It`s change current word and cont > 0, registre new item for concat
    if (currentword  != lastLetter  && totalLetter > 0 ) {
        
        compress = concatString(compress,lastLetter,totalLetter)
        
        lastLetter = currentword
        
        totalLetter = 0
    }
    totalLetter = totalLetter + 1

}
//After exit to loop we have registre te last letter computing
compress = concatString(compress,lastLetter,totalLetter)

print(compress)