1171

/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     ListNode *next;
 *     ListNode() : val(0), next(nullptr) {}
 *     ListNode(int x) : val(x), next(nullptr) {}
 *     ListNode(int x, ListNode *next) : val(x), next(next) {}
 * };
 */
class Solution {
public:
    ListNode* removeZeroSumSublists(ListNode* head) {
        unordered_map<int, ListNode*> map;
        ListNode *dummy = new ListNode(0, head);
        map[0] = dummy;
        int sum = 0;
        while(head){
            sum += head->val;
            if(map.find(sum) != map.end()){
                ListNode* curr = map[sum]->next;
                int tsum = sum + curr->val;
                while(tsum != sum){
                    map.erase(tsum);
                    curr = curr->next;
                    tsum += curr->val;
                }
                map[sum]->next = head->next;
            }
            else{
                map[sum] = head;
            }
            head = head->next;
        }
        return dummy->next;
    }
};