Solve the Medium-level Merge Intervals coding interview problem online in Python & JavaScript. Run your code against real test cases in the browser and study worked examples. It covers arrays, sorting, and intervals. 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 Intervals – Solve Online in Python & JavaScript

Given a collection of intervals, merge any overlapping intervals.

## Problem

Given an array intervals where `intervals[i] = [start_i, end_i]`, merge all overlapping intervals, and return an array of the non-overlapping intervals that cover all the intervals in the input.

## Constraints
* `1 <= intervals.length <= 10^4`
* `intervals[i].length == 2`
* `0 <= start_i <= end_i <= 10^4`

## Example
```
Input: intervals = [[1, 3], [2, 6], [8, 10], [15, 18]]
Output: [[1, 6], [8, 10], [15, 18]]
Explanation: Since intervals [1, 3] and [2, 6] overlap, merge them into [1, 6].
```

- Given an array of intervals where each interval is represented as `[start, end]`, merge overlapping intervals.
- The goal is to return a list of non-overlapping intervals that cover all intervals in the input array.

Understanding the Problem

- Sort the intervals based on their starting values.
- This will make it easier to detect overlaps by ensuring that any overlapping intervals are adjacent.

Sort Intervals by Start Time

- Create an empty list `merged` to store the merged intervals.
- The list will eventually contain only the non-overlapping intervals.

Initialize Merged Intervals List

- For each interval, check if it overlaps with the last interval in the `merged` list.
- If it does overlap, merge the intervals by extending the end of the last interval in `merged`.
- If it doesn’t overlap, simply add it to `merged`.

Iterate Through Sorted Intervals

- After processing all intervals, return the `merged` list which contains only non-overlapping intervals.

Return Merged Intervals

- Edge cases include:
  - Only one interval, which should be returned as-is.
  - Non-overlapping intervals, where each interval is added to `merged` without modification.
  - Intervals that completely overlap each other.