Is Remove Zero Sum Consecutive Nodes from Linked List easy or hard?

The problem is rated Medium because it combines linked list pointer manipulation with the prefix sum technique. Developers familiar with prefix sums in arrays often find the concept straightforward, but applying it to linked lists requires careful pointer updates.

Remove Zero Sum Consecutive Nodes from Linked List Python/Java solution

Most implementations follow the same prefix sum logic across languages. Traverse the list, store prefix sums in a hash map mapping sum to node, then adjust node pointers in a second pass. This approach translates directly to Python, Java, C++, C#, and JavaScript.

How to solve Remove Zero Sum Consecutive Nodes from Linked List in O(n)?

Maintain a running prefix sum while traversing the list and store each sum in a hash map mapped to its latest node. If a prefix sum repeats, the nodes between the two occurrences sum to zero. Updating the previous node's next pointer removes the entire segment, allowing the algorithm to complete in linear time.

What is the best approach for Remove Zero Sum Consecutive Nodes from Linked List?

The most efficient approach uses prefix sums with a hash map. While traversing the linked list, store the latest node for each prefix sum. If the same prefix sum appears again, the nodes between them sum to zero and can be removed by updating pointers. This runs in O(n) time with O(n) extra space.

Is Remove Zero Sum Consecutive Nodes from Linked List asked at Google/Amazon/Meta?

Linked list problems involving prefix sums and hash maps are common in interviews at companies like Amazon, Google, and Meta. Variants of this problem test your ability to detect ranges using prefix sums and manipulate pointers efficiently in a linked list.

What data structure is used in Remove Zero Sum Consecutive Nodes from Linked List?

The optimal solution combines a linked list traversal with a hash map that stores prefix sums. The linked list handles node connections, while the hash map enables constant-time detection of previously seen sums to identify zero-sum ranges.

What is the time complexity of Remove Zero Sum Consecutive Nodes from Linked List?

The optimal prefix sum hash map solution runs in O(n) time because each node is processed a constant number of times. The space complexity is O(n) due to storing prefix sums in a hash map. A simpler iterative scanning approach exists but can take O(n²) time in the worst case.

Description Hints 3 Solution Video 23:53

1171. Remove Zero Sum Consecutive Nodes from Linked List

Medium53.3% acceptance6 companies

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 and 1000 nodes.
Each node in the linked list has -1000 <= node.val <= 1000.

Asked at 6 companies

Uber Bytedance Palo Alto Networks Bloomberg

Google Amazon

Topics

Hash Table Linked List

Hints open one at a time

Hint 1

Convert the linked list into an array.

Hint 2

While you can find a non-empty subarray with sum = 0, erase it.

Hint 3

Convert the array into a linked list.

23:53

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