puzzle.sc

def reverseInt(x: Int): Int = {
    x.toString.reverse.toInt
}

def palindromeNumberEquation(x:Int, y:Int): Boolean = {
    reverseInt(x) == x*y
}

def differentDigitsInt(x: Int, y: Int): Boolean = {
    x.toString.groupBy(c => c).map(m => m._2.length).sum == y
}

def puzzle(x: Int, digits:Int, factor:Int): Boolean = {
    differentDigitsInt(x, digits) match {
        case true => palindromeNumberEquation(x, factor)
        case _ => false
    }
}

def findFirstNumberSolvingEquation(x:Int, digits:Int, factor: Int): Boolean = {
    puzzle(x, digits, factor) match {
        case true  => println("Number x= " + x + " * " + factor + " = " + reverseInt(x))
                      true
        case false => findFirstNumberSolvingEquation(x+1, digits, factor)
    }
}

findFirstNumberSolvingEquation(10000, 5, 4)

https://curiosity.com/topics/can-you-solve-the-abcde-math-puzzle-curiosity/?utm_source=androidapp