82. Remove Duplicates from Sorted List II

Given a sorted linked list, delete all nodes that have duplicate numbers, leaving only distinct numbers from the original list.

Example 1:

Input: 1->2->3->3->4->4->5
Output: 1->2->5

Example 2:

Input: 1->1->1->2->3
Output: 2->3

AC code:

/**
 * 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) {
        ListNode* dummy = new ListNode(0);
        dummy->next = head;
        ListNode* p = dummy;
        while (p->next != NULL && p->next->next != NULL) {
            if (p->next->val == p->next->next->val) {
                int sameNum = p->next->val;
                while (p->next != NULL && p->next->val == sameNum)
                    p->next = p->next->next;
            } else {
                p = p->next;
            }
        }
        return dummy->next;
    }
};

Runtime: 4 ms, faster than 100.00% of C++ online submissions for Remove Duplicates from Sorted List II.