Remove all elements from a linked list of integers that have value val.

Example

Given: 1 --> 2 --> 6 --> 3 --> 4 --> 5 --> 6, val = 6

Return: 1 --> 2 --> 3 --> 4 --> 5

/** * Definition for singly-linked list. * struct ListNode { *     int val; *     ListNode *next; *     ListNode(int x) : val(x), next(NULL) {} * }; */class Solution {public:    ListNode* removeElements(ListNode* head, int val) {        if(!head)            return head;        ListNode * Dummy = new ListNode(-1);        Dummy->next = head;                ListNode * pre = Dummy;        ListNode * p = head;        while(p){            if(p->val != val){                pre = p;                p = p->next;            }            else{                pre->next = p->next;                p = p->next;            }        }                return Dummy->next;        delete Dummy;            }};