How to Identify Patterns in DSA Problems? | 6 Type of Interval Problems Asked in FAANG Interviews

Summary

The video emphasizes the importance of solving different types of problems, rather than focusing on the quantity of problems solved, especially in technical interviews for companies like Amazon, Google, and Facebook. It introduces the topic of interval problems, which are less discussed but frequently asked in interviews. The speaker explains six key types of interval-based problems, highlighting patterns that can help candidates crack interviews. Additionally, he shares resources for further learning and invites viewers to suggest topics for future videos. The content encourages a deeper understanding of problem patterns rather than rote memorization.

Takeaways

• 💡 Focus on the variety of problem types over sheer number solved. Understanding different patterns is more crucial for cracking interviews.
• 🧩 Interval problems are underrepresented in resources but frequently asked in interviews for top tech companies like Google, Amazon, and Facebook.
• 📚 Solve fewer problems but focus on different patterns to gain a broader understanding of the subject and improve interview readiness.
• 🔀 Key patterns discussed include merging sorted intervals, inserting new intervals, and finding overlaps between intervals.
• 🧮 For merging intervals, sort by the start value and merge overlapping intervals based on specific conditions (current start ≤ previous end).
• 📝 Pattern four, involving minimum platforms required or meeting rooms required, is one of the easiest and most important patterns to solve in interviews.
• 🚗 Carpooling and employee free time problems involve maintaining a balance between the start and end of multiple intervals.
• 🔢 Learn and apply key formulas for merging intervals and finding intersections. These are crucial for solving interval-related problems.
• 📊 Tree maps and special functions like floor key and ceiling key are essential for handling complex queries in certain interval problems (e.g., calendar problems).
• 🔎 Solving 3-4 problems per pattern is sufficient to master the concept without overwhelming yourself with redundant problem-solving.

Q & A

What is the main message the speaker wants to convey about solving problems for interviews?

The speaker emphasizes that solving a wide variety of problem types is more important than the sheer number of problems solved. Understanding different problem patterns and being able to apply those patterns in interviews is key to success.

Why does the speaker focus on 'problems on intervals' in the video?

The speaker highlights 'problems on intervals' because they are frequently asked in interviews by top companies like Amazon, Google, and Facebook, yet they are less discussed compared to other topics like dynamic programming or graphs.

What is the first type of interval problem discussed, and how is it solved?

The first type discussed is 'merge sorted intervals.' In this problem, you're given a list of intervals and need to merge overlapping intervals. The solution involves sorting the intervals based on the starting point and merging them using a simple condition.

How is the second type of interval problem, inserting a new interval, related to the first type?

The second type, 'inserting a new interval in a sorted interval,' is an extension of the first problem. It involves finding the right place to insert the new interval and then merging overlapping intervals similarly to the first problem.

What are the two important formulas discussed in the third type of interval problem?

In the third type of interval problem, two key formulas are mentioned: one for merging two intervals (determining the merged start and end) and another for finding the intersection of two intervals.

What is the fourth type of interval problem, and why is it considered important?

The fourth type is about calculating the 'minimum platforms required' or 'meeting rooms required.' It is a frequently asked and relatively easy problem that requires separating start and end times of intervals and applying a merging technique.

What is the approach for solving the 'minimum platforms required' problem?

The solution involves sorting the start and end times of intervals, then merging them to find the maximum overlap at any given time, which corresponds to the minimum number of platforms required.

What is the fifth type of interval problem, and how does it differ from previous types?

The fifth type involves maintaining a balance factor between the start and end of intervals to find gaps. An example problem is 'carpooling,' where you must ensure that the car’s capacity is not exceeded based on overlapping intervals.

What makes the sixth type of interval problem the hardest, and which company frequently asks it?

The sixth type is challenging because it involves multiple queries for inserting intervals, making it more complex than earlier types. Google has frequently asked this type of question in interviews over the last six months.

What advice does the speaker give regarding solving multiple problems from the same pattern?

The speaker advises solving three to four problems from each pattern to understand it well, rather than solving many repetitive problems. This approach helps in gaining a broader understanding of different problem types.