Question

in Scala programming, I need to solve the problem following,

sjok A little tricker. Make this function return true if every second entry in a list forms a palindrome. eg,List(99, 1,98, 2, 97, 2, 96, 2, 95, 1) is a palindrome because every second element forms List(1, 2, 2, 1) which is a palindrome You might find zipwithIndex and filter useful to extract every second element. You might also find it helpful to print out an intermediate result k/ def secondPalíndrome [T] (list :List [T]) : Boolean = { 7??

in order to pass the test class following,

could you please implement that function?

Answer 1

//Utility method for finding palindrome using reverse def isPalindrome[T](list: List[T]): Boolean = { list == list. Reverse } // Method to be implemented /* Example: list = List(1, 2, 3, 4, 5, 2) list.zipWithIndex will give list of Tuple 2 with first entry as element and second entry as index. List.zipWithIndex = List((1, 0), (2, 1), (3, 2), (4, 3), (5, 4), (2, 5)) filter(listTuple Rightarrow list Tuple._1) will map the first element of the tuple to a newList newList = List(2, 4, 2) passing this newList to isPalindrome will give us the desired output true. */ def secondPalindrome[T](list: List[T]): Boolean = { val newList = List.zipWithIndex.filter(ListTuple Rightarrow ListTuple._2 % 2 == 1). Map(ListTuple Rightarrow ListTuple._1) isPalindrome(newList) } output: println(secondPalindrome(List())) true println(secondPalindrome(List(1))) true println(secondPalindrome(List(1, 2))) true println(secondPalindrome(List(1, 1, 99, 2, - 99, 2, 103, 1))) true println(secondPalindrome(List(1, 1, 99, 2, - 99, 2, 103, 1, 567))) true println(secondPalindrome(List(1, 1, 99, 2, 3, - 99, 2, 103, 1, 567))) true

Output: