lintcode-Remove Linked List Elements-452

Remove all elements from a linked list of integers that have value val.

ÑùÀý

Given 1->2->3->3->4->5->3, val = 3, you should return the list as 1->2->4->5

class Solution {  
public:  
     
    ListNode *removeElements(ListNode *head, int val) {  
        if(!head)  
            return nullptr;  
        while(head&&head->val==val){
            ListNode *p=head;
            head=head->next;
            free(p);
        }      
        ListNode *ptr=head;  
        ListNode *q;  
        while(ptr){  
            if(ptr->val==val){  
                if(!ptr->next){  
                    q->next=NULL;  
                    free(ptr);  
                }else{  
                    ListNode *tmp=ptr->next;  
                    ptr->val=tmp->val;  
                    ptr->next=tmp->next;  
                    free(tmp);  
                }      
            }else{  
                q=ptr;  
                ptr=ptr->next;  
            }  
        }  
        return head;  
    }  
};