206--Reverse A Singly Linked List

LinedList Package; 

public class ReverseASinglyLinkedList { 
    // Solution a: iteration. 
    ListNode reverseList public (ListNode head) { 
        ListNode Previous = null; 
        ListNode Current = head; 
        the while (Current = null!) { 
            ListNode Next = current.next; 
            current.next = Previous; 
            Previous = Current; 
            Current = Next; 
        } 
        return Current ; 
    } 
        / ** 
         * Method II: recursive 
         * recursive and iterative actually thinking the same, is to deal with two nodes, so that the pointer between them reversed. 
         * But, iterative process from start to finish in turn, requires an additional pointer to the next node. 
         * Is recursively from the tail to the head, back when there will be a current node, so no additional pointer. 
         * Also note that: p head node is the entire list of the reversed after it was first found, there is no any treatment.
         * Rather than each time the nodes to process (reversal) of. 
         * / 
    Public ListNode reverseList2 (ListNode head) { 
        IF (head == null || head.next == null) 
            return head; 
        ListNode P = reverseList2 (head.next); 
        head.next.next = head; 
        head.next = null; 
        return P; 
    } 
}