LeetCode——remove-duplicates-from-sorted-list-ii

Question

Given a sorted linked list, delete all nodes that have duplicate numbers, leaving only distinct numbers from the original list.
For example,
Given1->2->3->3->4->4->5, return1->2->5.
Given1->1->1->2->3, return2->3.

Solution

判断当前节点和下一个节点是否相等，同时在开头添加了一个节点，因为开始的节点可能就是重复的，会被删除。

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* pNode = head;
        ListNode* tmp = new ListNode(0);
        tmp->next = pNode;
        ListNode* pre = tmp;
        while (pNode != NULL) {
            bool flag = false;
            while (pNode->next != NULL && pNode->val == pNode->next->val) {
                flag = true;
                pNode = pNode->next;
            }
            if (flag) {
                pre->next = pNode->next;
                pNode = pNode->next;
            } else {
                pre = pNode;
                pNode = pNode->next;
            }
        }
        return tmp->next;
    }
};