56.删除链表中重复的节点——剑指offer

题目描述

在一个排序的链表中，存在重复的结点，请删除该链表中重复的结点，重复的结点不保留，返回链表头指针。 例如，链表1->2->3->3->4->4->5 处理后为 1->2->5

/*
struct ListNode {
    int val;
    struct ListNode *next;
    ListNode(int x) :
        val(x), next(NULL) {
    }
};
*/
class Solution {
public:
    ListNode* deleteDuplication(ListNode* pHead)
    {
        ListNode* res = new ListNode(-1);
        ListNode* pre = res;
        res->next = pHead;
        ListNode* s = pHead;
        ListNode* cur =pHead;
        while(cur != nullptr && cur->next != nullptr){
            cur = cur->next;
            if(cur->val == s->val) {
                cur = cur->next;
                while(cur && cur->val == s->val){
                    cur = cur->next;
                }
                pre->next = cur;
                s = cur;
            }
            else {
                pre = s;
                s = cur;
            }
        }
        return res->next;
    }
};