算法通关村第二关——终于学会链表反转了

建立虚拟节点进行链表反转

    public static ListNode reverseList(ListNode head){
        ListNode ans = new ListNode(-1);
        ListNode cur = head;

        while (cur != null){
            ListNode next = cur.next;
            cur.next = ans.next;
            ans.next = cur;
            cur = next;
        }
        return ans.next;
    }

直接操作链表

    public ListNode reverseList1(ListNode head){
        ListNode prev = null;
        ListNode cur = head;

        while (cur != null){
            ListNode next = cur.next;
            cur.next = prev;
            prev = cur;
            cur = next;
        }
        return prev;
    }