Is Remove Linked List Elements easy or hard?

Remove Linked List Elements is categorized as an Easy problem on LeetCode. It mainly tests understanding of linked list traversal and pointer updates, making it a common starter problem for practicing linked list manipulation.

Remove Linked List Elements Python/Java solution

Python and Java solutions typically implement the dummy head technique. Create a sentinel node pointing to the head, iterate through the list, and bypass nodes whose value matches the target. The same logic applies across C++, C#, and JavaScript implementations.

How to solve Remove Linked List Elements in O(n)?

Traverse the linked list while maintaining a previous pointer. If the current node's value equals the target value, update prev.next to skip that node. Using a dummy head before the real head simplifies edge cases and guarantees a single O(n) pass.

What is the best approach for Remove Linked List Elements?

The iterative approach using a dummy head node is the most reliable solution. It traverses the list once and removes nodes by updating pointers, achieving O(n) time and O(1) extra space. The dummy node avoids edge cases where the head itself needs to be removed.

Is Remove Linked List Elements asked at Google/Amazon/Meta?

Linked list deletion and pointer manipulation problems are common across major tech interviews including Amazon, Google, and Meta. Variants of this question frequently appear in early interview rounds to evaluate basic data structure fundamentals.

What data structure is used in Remove Linked List Elements?

The problem operates on a singly linked list. The key operations involve pointer traversal, node comparison, and pointer reassignment to remove nodes without breaking the list structure.

What is the time complexity of Remove Linked List Elements?

Both common solutions run in O(n) time because every node in the linked list is visited once. The iterative dummy-head method uses O(1) extra space, while the recursive approach uses O(n) stack space due to recursive calls.

Description Solution Video 7:51

203. Remove Linked List Elements

Easy55.3% acceptance9 companies

Given the head of a linked list and an integer val, remove all the nodes of the linked list that has Node.val == val, and return the new head.

Example 1:

Input: head = [1,2,6,3,4,5,6], val = 6
Output: [1,2,3,4,5]

Example 2:

Input: head = [], val = 1
Output: []

Example 3:

Input: head = [7,7,7,7], val = 7
Output: []

Constraints:

The number of nodes in the list is in the range [0, 10⁴].
1 <= Node.val <= 50
0 <= val <= 50

Asked at 9 companies

Arista Networks Bloomberg

Google Amazon Microsoft Meta Oracle Apple

TCS

Topics

Linked List Recursion

7:51

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LanguageLoading editor…

1# Definition for singly-linked list.
2# class ListNode:
3#     def __init__(self, val=0, next=None):
4#         self.val = val
5#         self.next = next
6class Solution:
7    def removeElements(self, head: Optional[ListNode], val: int) -> Optional[ListNode]:
8        

Starter codePython 3Spaces: 4

Examples

Case 1Case 2Case 3

Input

[1,2,6,3,4,5,6]
6

Input

[]
1

Input

[7,7,7,7]
7

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