reverse linked list

rev_linked_list.kt

//
// Recursively change each node of the linked list such that next
// is the last node seen during a linear scan of the linked list.
//
class Solution {
    fun reverseList(head: ListNode?): ListNode? {
        fun go(node: ListNode? = head, last: ListNode? = null): ListNode? {
            var next = node?.next
            node?.next = last
            if (next == null)
                return node
            return go(next, node)
        }
        return go()
    }
}