203 Remove Linked List Elements

<p style="margin-top: 0px; margin-bottom: 10px; box-sizing: border-box; color: rgb(51, 51, 51); font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif; font-size: 14px; line-height: 30px;">Remove all elements from a linked list of integers that have value <span style="box-sizing: border-box; font-weight: 700;">val</span>.</p><p style="margin-top: 0px; margin-bottom: 10px; box-sizing: border-box; color: rgb(51, 51, 51); font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif; font-size: 14px; line-height: 30px;"><span style="box-sizing: border-box; font-weight: 700;">Example</span><br style="box-sizing: border-box;" /><span style="box-sizing: border-box;"><span style="box-sizing: border-box; font-weight: 700;">Given:</span></span> 1 --> 2 --> 6 --> 3 --> 4 --> 5 --> 6, <span style="box-sizing: border-box; font-weight: 700;">val</span> = 6<br style="box-sizing: border-box;" /><span style="box-sizing: border-box;"><span style="box-sizing: border-box; font-weight: 700;">Return:</span></span> 1 --> 2 --> 3 --> 4 --> 5</p>

/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     struct ListNode *next;
 * };
 */
struct ListNode* removeElements(struct ListNode* head, int val) 
{
    struct ListNode *p1 = NULL, *p2 = NULL, *p_ret = NULL;
    
    while(head && head->val == val)
        head = head->next;
    if(head == NULL)
        return head;
    
    p_ret = head;
    p1 = head;
    p2 = p1->next;
    
    while(p2)
    {
        if(p2->val == val)
        {
            p1->next = p2->next;
            p2 = p2->next;
        }
        else
        {
            p1 = p1->next;
            p2 = p2->next;
        }
    }
    
    return p_ret;
}

63 / 63 test cases passed.	Status:  Accepted
Runtime:  13 ms