Solve the Medium-level Redundant Connection coding interview problem online in Python & JavaScript. Run your code against real test cases in the browser and study worked examples. It covers graph and union find. 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).

Redundant Connection – Solve Online in Python & JavaScript

Kth Largest Element in an Array

Rotting Oranges

Find the edge that creates a cycle in an otherwise tree-shaped graph.

A connected undirected graph started as a tree, then one extra edge was added. Return the last input edge that can be removed to restore a tree.

## Example
```
Input: {"edges":[[1,2],[1,3],[2,3]]}
Output: [2,3]
```

**Constraints**
- 3 <= edges.length <= 1000
- There are no duplicate edges or self-loops.
- Node labels are from 1 through n.

**Follow-up**
How do path compression and union by rank improve performance?

- Identify the required output and the state that changes.
- Use the examples to rule out tempting but incorrect interpretations.

Understand the Goal

- This problem is best exposed by Disjoint-set union detects an edge joining already-connected nodes.
- Maintain only the state needed for the next operation.

Choose the Core Pattern

- Process each state once when possible.
- Record state before scheduling dependent work to avoid duplicates.

Build the Algorithm

- Verify the smallest input, impossible cases, and repeated values where allowed.
- Keep output ordering deterministic.