Formatted question description: https://leetcode.ca/all/1171.html
1171. Remove Zero Sum Consecutive Nodes from Linked List
Level
Medium
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: [1]
Constraints:
 The given linked list will contain between
1
and1000
nodes.  Each node in the linked list has
1000 <= node.val <= 1000
.
Solution
Create a dummyHead
and set dummyHead.next = head
. Initialize temp = dummyHead
. Each time delete zero sum consecutive nodes starting from temp.next
. If there are nodes that are deleted, set temp.next
to be the next node after deletion. Otherwise, set temp = temp.next
.
Finally, return dummyHead.next
.

/** * Definition for singlylinked list. * public class ListNode { * int val; * ListNode next; * ListNode(int x) { val = x; } * } */ class Solution { public ListNode removeZeroSumSublists(ListNode head) { ListNode dummyHead = new ListNode(0); dummyHead.next = head; ListNode temp = dummyHead; while (temp != null) { ListNode zeroLast = removeZero(temp.next); if (zeroLast == null) temp = temp.next; else temp.next = zeroLast.next; } return dummyHead.next; } public ListNode removeZero(ListNode node) { ListNode temp = node; int sum = 0; while (temp != null) { sum += temp.val; if (sum == 0) return temp; else temp = temp.next; } return null; } }

// OJ: https://leetcode.com/problems/removezerosumconsecutivenodesfromlinkedlist/ // Time: O(N) // Space: O(N) class Solution { public: ListNode* removeZeroSumSublists(ListNode* head) { ListNode dummy; dummy.next = head; unordered_map<int, ListNode*> m{ {0, &dummy} }; auto node = head; int sum = 0; while (node) { sum += node>val; if (m.count(sum)) { int s = sum; for (auto p = m[sum]>next; p != node; p = p>next) { s += p>val; m.erase(s); } m[sum]>next = node>next; if (m.count(sum)) { } else { m[sum] = node; } node = node>next; } return dummy.next; } };

# 1171. Remove Zero Sum Consecutive Nodes from Linked List # https://leetcode.com/problems/removezerosumconsecutivenodesfromlinkedlist/ # Definition for singlylinked list. # class ListNode: # def __init__(self, val=0, next=None): # self.val = val # self.next = next class Solution: def removeZeroSumSublists(self, head: ListNode) > ListNode: prefix = 0 seen = {} seen[0] = dummy = ListNode(0) dummy.next = head while head: prefix += head.val seen[prefix] = head head = head.next prefix = 0 head = dummy while head: prefix += head.val head.next = seen[prefix].next head = head.next return dummy.next