• 算法
    • 1.设置伪结点，方便处理
    • 2.双指针prev和curr
    • 3.当遇到当前节点值和下一节点值相等的节点时，进行while循环找到下一个不相等的节点，挂到prev节点上
    • 4.当遇到当前节点值和下一节点值不相等的节点时，prev和curr都移动到下一个节点接着遍历就行 
public ListNode deleteDuplicates(ListNode head) {
    ListNode dummy = new ListNode(-1);
    dummy.next = head;

    ListNode prev = dummy;
    ListNode curr = head;
    while (curr != null && curr.next != null) {
        if (curr.val == curr.next.val) {
            ListNode temp = curr.next;
            while (temp != null && temp.val == curr.val) {
                temp = temp.next;
            }
            prev.next = temp;
            curr = temp;
        } else {
            prev = prev.next;
            curr = curr.next;
        }
    }
    return dummy.next;
}