C++ Interview with a FAANG engineer

Interview Summary

Problem type
Buildings with an ocean view

Interview question
There are n buildings in a line. You are given an integer array heights of size n that represents the heights of the buildings in the line.
The ocean is to the right of the buildings. A building has an ocean view if the building can see the ocean without obstructions. Return a list of indices (0-indexed) of buildings that have an ocean view, sorted in increasing order.

Example 1:
Input: heights = [4,2,3,1]
Output: [0,2,3]
Explanation: Building 1 does not have an ocean view because building 2 is taller.

Example 2:
Input: heights = [4,4,1]
Output: [1, 2]

Interview Feedback

Feedback about Digital Fresh (the interviewee)

Advance this person to the next round?
Yes
How were their technical skills?
3/4
How was their problem solving ability?
3/4
What about their communication ability?
4/4

Strengths:

• Communication:
  • Positive, affable; seems great to work with
  • Attentive listener and open to hints while being proactive to find solutions (and persistent)
• Time management:
  • Great job in general on asking clarifying questions, sharing thought process for solution space, and implementing code, especially on the first problem
• Technical:
  • Very comfortable with arrays
  • Time and space complexity spot on
  • Overall looks solid on general c++

Potential areas of improvement

• Problem solving:
  • For the second problem with skylines, had more components and nuances to it: recommend to walk through one or two complete examples
  • In the examples, articulate more on what your solution should track (e.g., running sum vs. current max score)
• Technical:
  • Using "&" in method signature
  • Instead of reversing an array, you could use STL's "reverse"
  • Proactively write down Time and Space complexity at the end of the solution
  • Practice iterating through hash maps/dictionaries in C++

Interview Transcript

Digital Fresh: Yeah, I'm looking for like an E3 level. I have two years of experience, but yeah, I'm still looking for more of an entry level role.

Stochastic Panda: Excellent. So let's move on to the interview question. Here we go.

• For the first interview question, what would you say is the time and space complexity?

Digital Fresh: Time is O(N) and Space is also O(N).

Stochastic Panda: Okay, great. I think this is looking good. Let's move on to one more question and let's see if it's okay. I'll paste the question starting now. Here we go.

Second Problem: The Skyline of Buildings

Interview question
You are given an integer array heights of size n. Each element height[i] represents the height of the ith building. The skyline is valid if it meets the following conditions: The first and last building in the skyline have the same height. Return the maximum possible score of some valid skyline after demolishing buildings.

• Example 1: Input: [4,3,4] → Output: 4
  • Example reasoning: The valid skyline is simply the two 4s on either end.

Expected Output

For both interviews, it is expected that a candidate should clarify the output they are seeking.

Feedback about Stochastic Panda (the interviewer)

• Would you want to work with this person?
  Yes
• Overall performance I would give…
  4/4

Closing Remarks

• If you feel you could have done something better on the second question ask your mentor how you might solidify your code.

• Explore resources available on Leetcode for practice.