【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(0);
        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;
    }
};