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class Solution {
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 public:
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  ListNode *removeZeroSumSublists(ListNode *head) {
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    unordered_map<int, ListNode *> m; // {prefix -> node}
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    ListNode *dummy = new ListNode(0);
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    ListNode *cur = dummy;
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    dummy->next = head;
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    int prefix = 0;
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    while (cur) {
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      prefix += cur->val;
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      if (m[prefix] != NULL) {
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        ListNode *t = m[prefix]->next;
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        int sum = prefix;
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        sum += t->val;
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        while (sum != prefix) {
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          m.erase(sum);
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          t = t->next;
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          sum += t->val;
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        }
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        m[prefix]->next = cur->next;
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      } else
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        m[prefix] = cur;
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      cur = cur->next;
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    }
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    return dummy->next;
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  }
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};