<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]:
        
#         run = ListNode(0, head)
#         ans = run
        
#         while run:
#             runsum = 0
#             nxt = run.next
#             while nxt:
#                 runsum += nxt.val
#                 if runsum == 0:
#                     run.next = nxt.next
#                 nxt = nxt.next
#             run = run.next
            
#         return ans.next

        run = ListNode(0, head)
        ans = run
        
        sumdict = {}
        runsum = 0
        
        while run:
            runsum += run.val
            if runsum in sumdict:
                prev = sumdict[runsum]
                del_head = prev.next
                
                tmpsum = runsum + del_head.val
                while tmpsum != runsum:
                    del sumdict[tmpsum]
                    del_head = del_head.next
                    tmpsum += del_head.val
                
                
                sumdict[runsum].next = run.next
            else:
                sumdict[runsum] = run
            run = run.next
            
        return ans.next
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