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

 

题目很简单，注意链表首结点有可能更改时，需新建preHead结点，或者使用二维指针的编程方法。

1 /** 2  * Definition for singly-linked list. 3  * struct ListNode { 4  *     int val; 5  *     ListNode *next; 6  *     ListNode(int x) : val(x), next(NULL) {} 7  * }; 8  */ 9 class Solution {10 public:11     ListNode* removeElements(ListNode* head, int val) {12         if (head == NULL)13             return head;14             15         ListNode* prehead = new ListNode(0);16         prehead->next = head;17         ListNode* curNode = prehead;18         19         while (curNode->next != NULL) {20             if (curNode->next->val == val)21                 curNode->next = curNode->next->next;22             else23                 curNode = curNode->next;24         }25         26         head = prehead->next;27         delete prehead;28         return head;29     }30 };