[leetcode] Remove Linked List Elements

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

Credits:

Special thanks to @mithmatt for adding this problem and creating all test cases.

Have you met this question in a real interview?

/**
* 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)
{
ListNode *pre_ptr = NULL, *cur_ptr = head;

while(cur_ptr)
{
if(cur_ptr->val == val)
{
if(NULL == pre_ptr)
{
head = head->next;
delete cur_ptr;
cur_ptr = head;
}
else
{
pre_ptr->next = cur_ptr->next;
delete cur_ptr;
cur_ptr = pre_ptr->next;
}
}
else
{
pre_ptr = cur_ptr;
cur_ptr = cur_ptr->next;
}
}

return head;
}
};