Solve the Medium-level Clone Graph coding interview problem online in Python & JavaScript. Run your code against real test cases in the browser and study worked examples. It covers graph, depth first search, breadth first search, and hashmap. 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).

Clone Graph – Solve Online in Python & JavaScript

Pacific Atlantic Water Flow

Reorder List

Deep-copy a connected graph from its adjacency-list representation.

Given a 1-indexed undirected graph as adjacency rows, return an independent adjacency-list copy with the same neighbor order.

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

## Constraints
- 0 <= number of nodes <= 100
- No duplicate neighbors or self-loops

## Follow-up
In a node-object implementation, why must the clone map be filled before recursing?

The key pattern is: DFS copies each vertex and adjacency row once. 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.