LintCode - Remove Duplicates from Sorted List II Show result

Web Link

http://www.lintcode.com/en/problem/remove-duplicates-from-sorted-list-ii/

Description

Given a sorted linked list, delete all nodes that have duplicate numbers, leaving only distinct numbers from the original list.
Example
Given 1->2->3->3->4->4->5, return 1->2->5.
Given 1->1->1->2->3, return 2->3.

Code - C++

/**
 * Definition of ListNode
 * class ListNode {
 * public:
 *     int val;
 *     ListNode *next;
 *     ListNode(int val) {
 *         this->val = val;
 *         this->next = NULL;
 *     }
 * }
 */
class Solution{
public:
    /**
     * @param head: The first node of linked list.
     * @return: head node
     */
    ListNode * deleteDuplicates(ListNode *head) {
        // write your code here
        if (head == NULL || head->next == NULL) {
            return head;
        }
        ListNode* dummy = new ListNode(0);
        dummy->next = head;
        head = dummy;
        while (head->next != NULL && head->next->next != NULL) {
            if (head->next->val == head->next->next->val) {
                int val = head->next->val;
                while (head->next != NULL && head->next->val == val) {
                    head->next = head->next->next;
                }
            } else {
                head = head->next;
            }
        }
        return dummy->next;
    }
};

Tips

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