C++ 代码

/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     ListNode *next;
 *     ListNode(int x) : val(x), next(NULL) {}
 * };
 */
class Solution {
public:
    ListNode* filterList(ListNode* head) {
        if(head==NULL) return head;
        unordered_map<int,int> h;
        auto p=head;
        h[abs(p->val)]++;
        while(p){
            if(p->next){

                if(h[abs(p->next->val)]>0){
                    p->next=p->next->next;
                    continue;
                }
            }
            p=p->next;
            if(p) h[abs(p->val)]++;
        }
        return head;
    }
};