删除排序链表中的重复元素

class Solution {
public:
    ListNode* deleteDuplicates(ListNode* head) {
        if(!head||!head->next)return head;
        ListNode*left=head;
        ListNode*right=left->next;
        while(right){
            while(right->next&&right->val==left->val)right=right->next;
            if(!right->next){
                if(right->val==left->val){
                    left->next=nullptr;
                    return head;
                }
                else{
                    left->next=right;
                    return head;
                }
            }
            if(right){
                left->next=right;
                left=right;
                right=right->next;
            }
        }
        return head;
    }
};