## Description

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

After doing so, return the head of the final linked list.  You may return any such answer.

(Note that in the examples below, all sequences are serializations of ListNode objects.)

## Example 1

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

## Example 2

Input: head = [1,2,3,-3,4]
Output: [1,2,4]

## Example 3

Input: head = [1,2,3,-3,-2]
Output: 

## Constraints

• The given linked list will contain between 1 and 1000 nodes.
• Each node in the linked list has -1000 <= node.val <= 1000.

## Solution

if prefixSum[i] = prefixSum[j], erase from i to j.

## Code

### One Hash (WA)

One Hash is not Enough
with the example
[1,3,2,-3,-2,5,5,-5,1]

# Definition for singly-linked list.
# class ListNode:
#     def __init__(self, x):
#         self.val = x
#         self.next = None
class Solution:
def removeZeroSumSublists(self, head: ListNode) -> ListNode:
dummyNode = ListNode(0)
prefixSum = 0
prefixMap = {0:dummyNode}
while currentNode:
prefixSum += currentNode.val
if prefixSum in prefixMap:
prefixMap[prefixSum].next = currentNode.next
else:
prefixMap[prefixSum] = currentNode
currentNode = currentNode.next
return dummyNode.next

### One Hash with rollback

# Definition for singly-linked list.
# class ListNode:
#     def __init__(self, x):
#         self.val = x
#         self.next = None
class Solution:
def removeZeroSumSublists(self, head: ListNode) -> ListNode:
dummyNode = ListNode(0)
while currentNode:
prefixSum += currentNode.val
if prefixSum in prefixMap:
prefixMap[prefixSum].next = currentNode.next
currentNode, prefixSum = dummyNode.next, 0
prefixMap = {0:dummyNode}
else:
prefixMap[prefixSum] = currentNode
currentNode = currentNode.next
return dummyNode.next

### One Hash with loop

# Definition for singly-linked list.
# class ListNode:
#     def __init__(self, x):
#         self.val = x
#         self.next = None
class Solution:
def removeZeroSumSublists(self, head: ListNode) -> ListNode:
dummyNode = ListNode(0)
return dummyNode.next