LeetCode: Remove Duplicates from Sorted List II

忘了边界条件，少数次过

/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     ListNode *next;
 *     ListNode(int x) : val(x), next(NULL) {}
 * };
 */
class Solution {
public:
    ListNode *deleteDuplicates(ListNode *head) {
        // Start typing your C/C++ solution below
        // DO NOT write int main() function
        if (!head) return NULL;
        ListNode *pre = new ListNode(head->val-1);
        pre->next = head;
        ListNode *cur = pre;
        while (cur) {
            ListNode *p = cur->next;
            bool dup = false;
            while (p && p->next && p->val == p->next->val) {
                dup = true;
                p->next = p->next->next;
            }
            if (dup) cur->next = p->next;
            else cur = cur->next;
        }
        return pre->next;
    }
};

 C#

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     public int val;
 *     public ListNode next;
 *     public ListNode(int x) { val = x; }
 * }
 */
public class Solution {
    public ListNode DeleteDuplicates(ListNode head) {
        if (head == null) return null;
        ListNode pre = new ListNode(head.val-1);
        pre.next = head;
        ListNode cur = pre;
        while (cur != null) {
            ListNode p = cur.next;
            bool dup = false;
            while (p != null && p.next != null && p.val == p.next.val) {
                dup = true;
                p.next = p.next.next;
            }
            if (dup) cur.next = p.next;
            else cur = cur.next;
        }
        return pre.next;
    }
}