【Leetcode】【Easy】Remove Linked List Elements

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。

 /**
  * 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 == NULL)
             return head;

         ListNode* prehead = new ListNode();
         prehead->next = head;
         ListNode* curNode = prehead;

         while (curNode->next != NULL) {
             if (curNode->next->val == val)
                 curNode->next = curNode->next->next;
             else
                 curNode = curNode->next;
         }

         head = prehead->next;
         delete prehead;
         return head;
     }
 };