203. Remove linked list elements

Give you a list of the head node head And an integer val , Please delete all the contents in the linked list Node.val == val The node of , And back to New head node .
 

Example 1：

Input ：head = [1,2,6,3,4,5,6], val = 6
Output ：[1,2,3,4,5]
Example 2：

Input ：head = [], val = 1
Output ：[]
Example 3：

Input ：head = [7,7,7,7], val = 7
Output ：[]
 

Tips ：

The number of nodes in the list is in the range [0, 104] Inside
1 <= Node.val <= 50
0 <= val <= 50

source ： Power button （LeetCode）
link ：https://leetcode.cn/problems/remove-linked-list-elements
 

my ：

struct ListNode* removeElements(struct ListNode* head, int val){
    struct ListNode *p,*pr;
    if(head == NULL){
        return head;
    }
    while(head->val == val){
        if(head->next == NULL){
            return NULL;
        }
        head = head->next;
    }
    p = head;
    pr = p->next;
    while(pr){
        if(pr->val == val){
            if(pr->next == NULL){
                p->next = NULL;
            }
            else{
                p->next = pr->next;
            }
        }
        else{
            p = p->next;
        }
        pr = p->next;
    }
    return head;
}

official ：

struct ListNode* removeElements(struct ListNode* head, int val) {
    struct ListNode* dummyHead = malloc(sizeof(struct ListNode));
    dummyHead->next = head;
    struct ListNode* temp = dummyHead;
    while (temp->next != NULL) {
        if (temp->next->val == val) {
            temp->next = temp->next->next;
        } else {
            temp = temp->next;
        }
    }
    return dummyHead->next;
}