Event Overlap Detector

Problem Description

You are given a list of events, where each event is represented as an object with a start and an end time. Each time is a string in the HH:MM 24-hour format. All events occur within the same day, and each event's end time is strictly after its start time.

Your task is to implement a function that detects if any events overlap. If overlaps exist, the function should return a list (or any clear representation) of the overlapping events (for example, as pairs of events or their indices). If there are no overlaps, the function should indicate that the schedule is conflict-free.

Input

• An array (or list) of events. Each event is an object/dictionary with the following properties:
  • start: a string representing the event's start time (e.g., "09:00")
  • end: a string representing the event's end time (e.g., "10:30")

Output

• A representation of the detected overlapping events. This could be a list of pairs (or indices) that identify the conflicting events. If there are no conflicts, return an indication (such as a message or an empty list) that the schedule is conflict-free.

Example

For instance, given the following list of events:

[
  {"start": "09:00", "end": "10:00"},
  {"start": "09:30", "end": "11:00"},
  {"start": "11:30", "end": "12:30"}
]

The first and second events overlap. Your function should identify and return this conflict.

Constraints

• The input list will contain at least one event.
• Assume valid time formats are provided.

Design your algorithm with both correctness and efficiency in mind. Document your code appropriately and consider using helper functions if necessary.