pascal.kt

 fun pascal(c: Int, r: Int): Int  {
        require(c>=0,{"column must be larger than zero"})
        require(r>=0,{"row must be larger than zero"})

        return when {
            r == 0 -> 1
            r == 1 -> 1
            c == 0 -> 1
            c == r -> 1
            else -> pascal(c - 1, r - 1) + pascal(c, r - 1)
        }

    }