What is the brute force solution for Remove Zero Sum Consecutive Nodes from Linked List?

The brute force approach for Remove Zero Sum Consecutive Nodes from Linked List is Brute Force, with O(n²) time complexity and O(1) space complexity. The brute force approach involves repeatedly scanning the linked list to find and remove any consecutive nodes that sum to zero. This is simple but inefficient, as it may require multiple passes through the list. The optimal Optimal Solution approach improves this to O(n).

What algorithm or data structure is used to solve Remove Zero Sum Consecutive Nodes from Linked List?

Remove Zero Sum Consecutive Nodes from Linked List uses the following concepts: Hash Table, Linked List. The recommended patterns to study are: Hash Map, Array.

What are the interview tips for Remove Zero Sum Consecutive Nodes from Linked List?

Explain your thought process clearly while coding. Consider edge cases early in your solution. Practice explaining your code and logic as if teaching someone else.

What are common mistakes when solving Remove Zero Sum Consecutive Nodes from Linked List?

Not resetting the hashmap after removals, leading to incorrect results. Failing to handle edge cases, such as when the entire list sums to zero.

#1171

Remove Zero Sum Consecutive Nodes from Linked List

Medium

Hash TableLinked ListHash MapArray

LeetCode ↗

Approaches

Brute ForceOptimal

Complexity Comparison

	Brute Force	Optimal Solution★
Time	O(n²)	O(n)
Space	O(1)	O(n)

💡

Intuition

Time O(n)Space O(n)

The optimal solution uses a hashmap to keep track of cumulative sums and their corresponding nodes. This allows us to efficiently find and remove zero-sum sequences in a single pass.

⚙️

Algorithm

5 steps

1Step 1: Create a dummy node that points to the head of the list.
2Step 2: Initialize a hashmap to store cumulative sums and their corresponding nodes.
3Step 3: Traverse the list, updating the cumulative sum and checking if it exists in the hashmap.
4Step 4: If it exists, remove the nodes between the previous occurrence and the current node.
5Step 5: Continue until the end of the list, returning the modified list.

solution.py21 lines

1# Full working Python code
2class ListNode:
3    def __init__(self, val=0, next=None):
4        self.val = val
5        self.next = next
6
7def removeZeroSumSublists(head):
8    dummy = ListNode(0)
9    dummy.next = head
10    current = dummy
11    sum_map = {}
12    total = 0
13    while current:
14        total += current.val
15        if total in sum_map:
16            prev = sum_map[total]
17            prev.next = current.next
18        else:
19            sum_map[total] = current
20        current = current.next
21    return dummy.next

ℹ

Complexity note: The time complexity is O(n) because we traverse the list only once. The space complexity is O(n) due to the hashmap storing cumulative sums and their corresponding nodes.

1Using cumulative sums helps identify zero-sum sequences efficiently.
2A hashmap allows for quick lookups and updates during traversal.

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