82. 删除排序链表中的重复元素 II

82. 删除排序链表中的重复元素 II

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode() {}
 *     ListNode(int val) { this.val = val; }
 *     ListNode(int val, ListNode next) { this.val = val; this.next = next; }
 * }
 */
class Solution {
    public ListNode deleteDuplicates(ListNode head) {
        if (head == null)
            return null;
        if (head.next == null)
            return head;
        ListNode dummyNode = new ListNode();
        dummyNode.next = head;
        ListNode p = head, q = head.next;
        ListNode node = dummyNode;
        while (q != null) {
            if (p.val != q.val) {
                node = node.next;
                p = p.next;
                q = q.next;
            } else {
                while (q != null && p.val == q.val)
                    q = q.next;
                node.next = q;
                if (q == null || q.next == null)
                    break;
                p = q;
                q = q.next;
            }
        } 
        return dummyNode.next;
    }
}