反转链表

public class VerseLink {

//直接遍历一遍
public static ListNode verseLink(ListNode head){
    ListNode previous,current,post;
    previous = null;
    current = head;

    while (current != null){
        post = current.next;
        current.next = previous;
        previous = current;
        current = post;
    }
    head = prev;
    return head;
}

//递归反转
public static ListNode recursiveVerseLink(ListNode head){
    if(head  == null || head.next == null){
        return head;
    }

    ListNode newHead = recursiveVerseLink(head.next);//原链表的最后一个结点
    head.next.next = head;//从倒数第二个结点开始回溯,指针发生转向
    head.next = null;//断开原来指针

    return newHead;
}

public static void main(String[] args){
    Link link = new Link();
    link.add(1);
    link.add(2);
    link.add(3);
    link.add(4);
    Link.head = VerseLink.recursiveVerseLink(Link.head);
    link.print();
}
}