题目：

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

跟上一题有点像，不过多增加前面的一些判断，遍历链表的循环里的判断变为val。

class Solution {public:    ListNode* removeElements(ListNode* head, int val) {        if(!head) return NULL;        while (head->val == val){            head = head->next;            if(!head) return NULL;        }                ListNode* cur = head;                while (cur){            if (cur->next == NULL) break;            if (cur->next->val == val){                cur->next = cur->next->next;            }            else{                cur = cur->next;            }        }        return head;    }};