Delete Nodes from a Binary Tree (Java)

Watch someone solve the delete nodes from a binary tree problem in an interview with a Google engineer and see the feedback their interviewer left them. Explore this problem and others in our library of interview replays.

Java interview with a Google engineer: Delete nodes from tree - YouTube

Interview Summary

Problem type
Delete nodes from a binary tree

Interview question

Debug this piece of code.
We want to delete certain nodes from a binary tree. We have a function shouldDelete(TreeNode node) that returns true if we should delete that node, you can assume this function already exists.
Write a function deleteNodes(TreeNode root) that takes a binary tree which removes the nodes that should be deleted from the tree and returns a forest of trees.

Interview Feedback

Feedback about Kind Ibex (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?
3/4

You have a good methodical and logical approach to problem solving, I don't have any suggestion here, good job.
Communication:
Explain your approach to the interviewer before you start writing code, it is a good idea to bring up the time complexity of your solution as well.
Don't feel obligated to step through your code out loud.
Coding:
Keep your indentation consistent.
Use a helper function if you need to when writing recursive functions.
It is more typical to use an interface type for the return value of a function instead of a concrete type, e.g. List instead of ArrayList.

Feedback about Talking Fox (the interviewer)

Would you want to work with this person?
Yes

How excited would you be to work with them?
4/4

How good were the questions?
4/4

How helpful was your interviewer in guiding you to the solution(s)?
4/4

You were the first interviewer who focused more on the thought process than speed. It makes me feel better so thank you on that. You had a good exercise in the beginning to break the ice so that was good too.

Interview Transcript

Talking Fox: Hello.
Kind Ibex: Hi can you hear me alright?
Talking Fox: Hi. Is this a good time for you? It will take about 45 minutes.
Kind Ibex: Oh yeah, I was waiting for you.
Talking Fox: Okay so let's start by doing some introductions and then taking a look at some code.
Kind Ibex: Okay.
Talking Fox: So I can start by telling you a bit about myself. So I was a software engineer at Google for about six years. I worked a lot of the time in Geo, so I worked on like the Maps front end and I worked on the android client for location sharing.
Kind Ibex: Okay.
Talking Fox: So you can stay anonymous if you want or you can tell me a bit about yourself either.
Kind Ibex: So I actually work in Intel. I graduated last year and right now working in the devops team for a year. I have my essary interview day after at Google, so I am just trying to see if I can make it this time.
Talking Fox: Sure umm so for the essary interviews, you do like some coding interviews and then some other more like essary specific ones right?
Kind Ibex: Yeah but for me I think it's like, I don't have a lot of experience so it's just holding down.
Talking Fox: Oh, interesting.
Kind Ibex: One behavior, that's it. Leadership round.

... [the transcript continues]

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