<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>

from collections import defaultdict

# 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]:
        arr = [] 
        while head:
            arr.append(head.val)
            head = head.next

        cum_sum_map = {}
        cum_sum = 0
        start = 0

        while start < len(arr):
            cum_sum += arr[start]

            if cum_sum == 0:
                arr = arr[start + 1:]
                start = 0
                cum_sum_map.clear()
                cum_sum = 0
            elif cum_sum in cum_sum_map:
                prev_index = cum_sum_map[cum_sum]
                arr = arr[:prev_index + 1] + arr[start + 1:]
                start = prev_index + 1
                keys_to_remove = [key for key in cum_sum_map if cum_sum_map[key] > prev_index]
                for key in keys_to_remove:
                    del cum_sum_map[key]
            else:
                cum_sum_map[cum_sum] = start
                start += 1
        
        if not arr:
            return None
        
        head= ListNode(val=arr[0])
        curr = head
        for i in range(1,len(arr)):
            newNode = ListNode(arr[i])
            curr.next = newNode
            curr = curr.next
        
        return head
        
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