import cn.leekari.base.ListNode;

/**
 * @author leekari
 * @date 2020/10/12 16:56
 * @description
 */

/**
 * 链表反转
 */
public class ReverseList {

    public static ListNode ReverseList(ListNode head) {
        if (head == null) {
            return null;
        }
        ListNode pre = null;
        ListNode next = null;

        while (head != null) {
            next = head.next;
            head.next = pre;
            pre = head;

            head = next;
        }
        return pre;
    }

    public static void main(String[] args) {
        ListNode listNode = new ListNode(1);
        listNode.next = new ListNode(2);
        listNode.next.next = new ListNode(3);
        ListNode listNode1 = ReverseList(listNode);
        while (listNode1 != null) {
            System.err.println(listNode1.val);
            listNode1 = listNode1.next;
        }
    }
}