206-Reverse-Linked-List.scala

/**
 * Definition for singly-linked list.
 * class ListNode(_x: Int = 0, _next: ListNode = null) {
 *   var next: ListNode = _next
 *   var x: Int = _x
 * }
 */
object Solution {
    def reverseList(head: ListNode): ListNode = {
        if (head == null || head.next == null) {
            return head
        }
        
        val reversedListHead = reverseList(head.next)
        head.next.next = head
        head.next = null
        
        return reversedListHead
    }
}