203. Remove Linked List Elements

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/**
 * 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 NULL;
        
        ListNode *p=head;
        while(head!=NULL&&head->val==val)
        {
            head=head->next;
        }
        p=head; //deal with head node
        while(head!=NULL&&head->next!=NULL)
        {
           
            if(head->next->val==val)
            {
                head->next=head->next->next;
            }
            else
                head=head->next;
        }
        return p;
    }
};