1
var removeZeroSumSublists = function (head) {
2
  const dummyHead = new ListNode();
3
  dummyHead.next = head;
4
  let prev = dummyHead;
5
  let start = head;
6

7
  while (start != null) {
8
    let sum = 0;
9
    let tail = start;
10

11
    while (tail != null) {
12
      sum += tail.val;
13
      if (sum === 0) break;
14
      tail = tail.next;
15
    }
16

17
    if (tail) {
18
      prev.next = tail.next;
19
      start = tail.next;
20
    } else {
21
      prev = start;
22
      start = start.next;
23
    }
24
  }
25

26
  return dummyHead.next;
27
};