<p>Given the <code>head</code> of a linked list, we repeatedly delete consecutive sequences of nodes that sum to <code>0</code> until there are no such sequences.</p>

<p>After doing so, return the head of the final linked list.&nbsp; You may return any such answer.</p>

<p>&nbsp;</p>
<p>(Note that in the examples below, all sequences are serializations of <code>ListNode</code> objects.)</p>

<p><strong class="example">Example 1:</strong></p>

<pre>
<strong>Input:</strong> head = [1,2,-3,3,1]
<strong>Output:</strong> [3,1]
<strong>Note:</strong> The answer [1,2,1] would also be accepted.
</pre>

<p><strong class="example">Example 2:</strong></p>

<pre>
<strong>Input:</strong> head = [1,2,3,-3,4]
<strong>Output:</strong> [1,2,4]
</pre>

<p><strong class="example">Example 3:</strong></p>

<pre>
<strong>Input:</strong> head = [1,2,3,-3,-2]
<strong>Output:</strong> [1]
</pre>

<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>

<ul>
	<li>The given linked list will contain between <code>1</code> and <code>1000</code> nodes.</li>
	<li>Each node in the linked list has <code>-1000 &lt;= node.val &lt;= 1000</code>.</li>
</ul>

# Definition for singly-linked list.
# class ListNode:
#     def __init__(self, val=0, next=None):
#         self.val = val
#         self.next = next
class Solution:
    def removeZeroSumSublists(self, head: Optional[ListNode]) -> Optional[ListNode]:
        dummy = ListNode(0)
        dummy.next = head
        current = dummy

        while current.next:
            sum = 0
            start = current.next
            found = False
            while start:
                sum += start.val
                if sum == 0:
                    found = True
                    current.next = start.next
                    break
                start = start.next
            if not found:
               current = current.next
        return  dummy.next
            
        

    # def removeZeroSumSublists(self, head: Optional[ListNode]) -> Optional[ListNode]:
    #     dummy = ListNode(0)
    #     dummy.next = head
    #     prefix_sum = 0
    #     prefix_map = {0: dummy}
        
    #     current = head
    #     while current:
    #         prefix_sum += current.val
    #         if prefix_sum in prefix_map:
    #             # Remove nodes between prefix_map[prefix_sum] and current
    #             node = prefix_map[prefix_sum].next
    #             temp_sum = prefix_sum
    #             while node != current:
    #                 temp_sum += node.val
    #                 del prefix_map[temp_sum]
    #                 node = node.next
    #             prefix_map[prefix_sum].next = current.next
    #         else:
    #             prefix_map[prefix_sum] = current
    #         current = current.next
    
    #     return dummy.next




        
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