数据结构练习

public class ReverseLinkedList {

    public class ListNode {
        int val;
        ListNode next;

        ListNode(int x) {
            val = x;
        }
    }

    @Test
    public void test1() {

        ListNode a = new ListNode(1);
        ListNode b = new ListNode(2);
        ListNode c = new ListNode(3);
        ListNode d = new ListNode(4);
        ListNode e = new ListNode(5);

        a.next = b;
        b.next = c;
        c.next = d;
        d.next = e;
        e.next = null;

        ListNode listNode = reverseList2(a);
    }

    //迭代
    public ListNode reverseList2(ListNode head) {
        //判断是链表是否为空或者只有一个值的列表
        ListNode pre = null, cur = head;
        while (cur != null){
            ListNode next = cur.next;
            cur.next = pre;
            pre = cur;
            cur = next;
        }
        return pre;
    }

}