单向链表的反转

package constxiong.interview;

import constxiong.interview.SingleLinkedList.Node;

/**
 * 反转单向列表
 * 
 * @author ConstXiong
 * @date 2019-11-06 11:04:12
 */
public class TestReserveLinkedList {

    public static void main(String[] args) {
        SingleLinkedList<Integer> ll = new SingleLinkedList<Integer>();
        ll.add(1);
        ll.add(2);
        ll.add(3);
        ll.add(4);
        ll.add(5);
        ll.print();
        reverseLinkedList(ll);
        System.out.println();
        ll.print();
    }
    
    public static void reverseLinkedList(SingleLinkedList<Integer> ll) {
        Node<Integer> first = ll.first;
        reverseNode(first);
//        reverseNodeByRecursion(first);
        ll.first = ll.last;
        ll.last = first;
    }

    /**
     * 循环逆转节点指针
     * @param first
     */
    public static void reverseNode(Node<Integer> first) {
        Node<Integer> pre = null;
        Node<Integer> next = null;
        while (first != null) {
            next = first.next;
            first.next = pre;
            pre = first;
            first = next;
        }
        
    }

    /**
     * 递归逆转节点指针
     * @param head
     * @return
     */
    public static Node<Integer> reverseNodeByRecursion(Node<Integer> first) {
        if (first == null || first.next == null) {
            return first;
        }
        Node<Integer> prev = reverseNodeByRecursion(first.next);
        first.next.next = first;
        first.next = null;
        return prev;
    }
}