Interview Context
This was a highly challenging Bloomberg technical interview. The candidate had meticulously prepared their setup and environment a day in advance to ensure everything was perfect. To help the candidate perform at their best, CSOAHELP was ready in the background to provide real-time support and guide them in identifying key points of the problem. Known for its rigorous assessment of algorithmic skills and problem-solving approaches, Bloomberg's interviews are a golden opportunity for candidates to demonstrate their abilities. As the interview began, the interviewer promptly joined the virtual meeting and wasted no time in diving into the problem.
“Let’s start with a problem,” said the interviewer as the screen displayed the following question:
Interview Problem
[QABANK] Calendar Busy View
Problem Description:
Summary: Given list of events of a given day in a calendar, write an algorithm to return a list of busy view time slots. Busy view is created by consolidating adjacent and overlapping event time slots without showing details of individual events.
Details: Each event in the calendar has a start time, end time & some title. Events can start at any minute (granularity at the minute only, no seconds).
Sample inputs - Expected outputs:
Input: list of following events
(100,300, "Some Event") // 1:00 am to 3:00 am
(115,145, "Some Event")
(145,215, "Some Event")
(200,400, "Some Event")
(215,230, "Some Event")
(215,415, "Some Event")
(500,600, "Some Event")
(600,700, "Some Event")
Output: Based on above events, my busy view should show like this:
(100,415) // Busy from 1am to 4:15 am
(500,700) // Busy from 5am to 7am
Clarifying the Problem
The candidate carefully read the problem, nodded slightly, and then began to confirm the details with the interviewer: “If I understand correctly, I need to merge all overlapping or adjacent time intervals from the input events and return a consolidated list of busy time slots, right?”
During this process, CSOAHELP provided timely guidance, reminding the candidate to focus on critical aspects such as the definition of merging time slots and how to handle edge cases. These prompts helped the candidate concentrate on the core of the problem and articulate their clarifying questions more effectively.
The interviewer smiled and nodded, “Yes, that’s correct. Do you have any other clarifying questions before we proceed?”
The candidate thought for a moment and asked, “Should the output be sorted by start time? Also, is the input guaranteed to be sorted, or do I need to handle that myself?”
The interviewer seemed impressed: “Good question. Assume the input is unsorted, and yes, the output should be sorted by start time.”
Next, the candidate raised another important point: “What happens if an event has a start time equal to its end time, such as a zero-length duration?”
At this point, CSOAHELP provided an additional reminder, emphasizing that this could be a subtle but important boundary case. The candidate quickly picked up on the importance of this detail and asked the question.
The interviewer replied, “You can ignore such events for this problem. They don’t contribute to the busy view.”
Explaining the Approach
After confirming the problem details, the candidate took a deep breath and said, “Alright, I have a plan. Let me walk you through my approach.”
“Go ahead,” the interviewer gestured for them to proceed.
The candidate began explaining, “First, I will sort the input events based on their start times. Then, I will iterate through the sorted list and check if each event overlaps with the current merged interval. If it does, I will extend the current interval’s end time to include it. If it doesn’t, I will finalize the current interval and start a new one. Finally, I will return the list of merged intervals.”
As the candidate described their approach, CSOAHELP suggested emphasizing the importance of sorting and clearly defining merge conditions. The candidate incorporated this guidance and added, “Sorting is the crucial first step to ensure events are processed in chronological order, and the merging condition must cover all potential overlapping or adjacent scenarios.” This clarification made the candidate’s thought process even more convincing.
The interviewer nodded approvingly, “Sounds reasonable. What data structures are you planning to use?”
The candidate responded, “I will use a list to store the merged intervals. Sorting will take O(n log n), and merging will take O(n), so the overall complexity should be O(n log n).”
The interviewer gave an encouraging nod, “Great. Please proceed with the implementation. Let me know when you’re ready to go through it.”
Solving the Problem
The candidate began writing code as the interviewer observed silently. As the logic started to take shape, the candidate encountered a subtle challenge: how to handle adjacent but non-overlapping intervals, particularly in determining boundary conditions. At that moment, CSOAHELP prompted a helpful suggestion:
“Check if the end time of the current interval equals the start time of the next interval to merge adjacent slots.”
The candidate immediately incorporated this logic, maintaining a smooth flow in their explanation and implementation, while the interviewer remained unaware of the assistance.
After completing the implementation, the candidate reported back: “I’ve finished the implementation. Shall I walk you through the code?”
“Sure, let’s go through it step by step,” said the interviewer.
The candidate began with the sorting step and then moved on to explaining how intervals were merged. They pointed out the key logic: “The main condition here is to check whether the start time of the next event falls within or immediately after the current interval. If so, I update the end time. Otherwise, I finalize the current interval and start a new one.”
Handling Follow-Up Questions
The interviewer listened carefully and then posed a new question: “What if the input contains a very large number of events, say millions? Can your solution scale?”
Without hesitation, the candidate replied, “Since sorting is O(n log n) and merging is O(n), the algorithm should scale well. However, if memory usage becomes a concern, I could process the input in chunks or use external sorting for very large datasets.”
The interviewer nodded and asked, “What would you do if the input events were provided as a stream instead of a static list?”
After a brief pause for thought, the candidate answered, “In that case, I would use a priority queue to dynamically keep track of overlapping intervals. This would allow me to merge intervals on the fly as they arrive without needing to store the entire input.”
CSOAHELP added a timely suggestion: “Mention how a priority queue minimizes memory usage and is well-suited for real-time data.” The candidate seamlessly incorporated this point, saying, “Using a priority queue also ensures minimal memory usage, which is ideal for handling real-time data streams.”
The interviewer smiled, “That’s a good extension. I like your thought process.”
Behavioral Questions
In the final stage, the interviewer transitioned to behavioral questions: “Can you share an example of a time when you resolved a conflict within a team?”
The candidate paused briefly and then shared a thoughtful story about a collaborative experience, explaining how they mediated differing opinions and achieved consensus. Their response was genuine and well-structured, showcasing their teamwork and problem-solving skills.
Throughout this discussion, CSOAHELP provided keyword suggestions like “emphasize leadership and empathy” and “highlight measurable outcomes,” helping the candidate articulate their experiences effectively.
Conclusion
As the interview concluded, the candidate exhaled a sigh of relief. The interviewer said, “Thank you for your time. I enjoyed our discussion and appreciated your approach to solving the problem.”
The interview had tested not only their technical prowess but also their communication and adaptability. Behind the scenes, CSOAHELP had been an invaluable ally, ensuring the candidate stayed confident and composed while navigating complex challenges.
经过csoahelp的面试辅助，候选人获取了良好的面试表现。如果您需要面试辅助或面试代面服务，帮助您进入梦想中的大厂，请随时联系我。
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