Solve the Easy-level Merge Two Sorted Lists coding interview problem online in Python & JavaScript. Run your code against real test cases in the browser and study worked examples. It covers linked list, two pointers, and recursion. Read the step-by-step solution and complexity analysis. Java starter code is also included for reference (no in-browser JVM yet, so it can't be run here).

Merge Two Sorted Lists – Solve Online in Python & JavaScript

Linked List Cycle

Lowest Common Ancestor of a BST

Merge two sorted linked lists by rewiring their nodes.

Merge two ascending linked lists and return the head of one sorted node chain.

## Example
```json
Input: {"list1":[1,2,4],"list2":[1,3,4]}
Output: [1,1,2,3,4,4]
```

## Constraints
- 0 <= total nodes <= 100
- -100 <= node value <= 100
- Both lists are sorted

## Follow-up
Compare iterative O(1)-space merging with recursive merging.

## Execution note
Java/Go/Rust don't support this problem's ListNode/TreeNode structure yet — the starter is reference-only. Try Python or JavaScript to run and submit.

The key pattern is: Two pointers splice the smaller next node. Identify the state and invariant before coding.

Recognize the Pattern

Advance one state transition at a time. Mark or update state before exploring dependent work.

Build the Algorithm

Test empty or minimal input, skewed shapes, duplicates where allowed, and impossible outcomes.