LeetCode Problem #203 — Remove Linked List Elements Solve LeetCode Remove Linked List Elements using PHP and Two Pointers. This solution finds the optimal result using Two Pointer Convergence & Scanning in O(n) time.
| Property | Value |
|---|---|
| Problem | Remove Linked List Elements |
| LeetCode | #203 |
| Difficulty | Easy |
| Language | PHP |
| Algorithm | Two Pointer Convergence & Scanning |
| Data Structure | Array |
| Pattern | Two Pointers |
| Time Complexity | O(n) |
| Space Complexity | O(1) |
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 .
Use two pointers moving toward each other or in parallel to process elements in a single pass without quadratic nested loops.
We iterate through the input using Pointer Traversal & Node Manipulation. By maintaining state efficiently in a Linked List, we eliminate redundant operations and process each element in optimal time.
- Initialize state variables / data structure (Array).
- Process elements sequentially using Two Pointer Convergence & Scanning.
- Validate boundary conditions and return optimal result.
Consider the standard input for Remove Linked List Elements. Applying Two Pointer Convergence & Scanning yields the target result step by step.
- Time Complexity: O(n)
- Space Complexity: O(1)
Two Pointers
- Two Pointers
- Array
- Sorting
PHP
By utilizing Two Pointers, each element is processed efficiently, ensuring optimal performance while avoiding unnecessary re-computations.
- Failing to sort the array when ordering is required.
- Not skipping duplicate elements leading to non-unique pairs.
- Pointer out-of-bounds errors on edge inputs.
- Tests: In-place array traversal, duplicate elimination, and pointer convergence.
- Follow-up: Can this approach be extended to 3Sum or 4Sum variants?