Live Annotated Coding Interviews: SQL, Python and Javascript
Tags: hiring, sql, python, javascript
Published: 2020-05-04 20:14:32

This recording comes from a Youtube Live Stream in which I interview two amazing candidates on the spot, and explain what parts of their answers work, and what else they can do and say to impress interviewers and level up. For each candidate, we start by looking at the jobs they're applying for, and I guess what kings of interviews and questions they'll likely encounter. Then I ask them questions. We spend time digging into SQL, Python and Javascript questions from Leetcode.

Visit the Youtube replay to see the accompanying live stream chat:
{% youtube JbPY__PTBQY %}

# Data Science

I start with Robert, a data scientist with one year of experience in SQL and Python Pandas who is applying to Data Quality Analyst positions. 

We go through some introductory behavioral questions, and explain what the interviewer is really looking for:

- Introduce yourself
- Why this transition?
- Why this company and role?

Then we move on to the technical questions:

- How would you show certain data from this SQL database? How will the pulled data look different if you used JOIN instead of LEFT JOIN?

# Graduating Software Engineer

Next up is Dami, a software engineering student who is graduating this year and looking for a SWE position at Facebook or similar.

After reviewing his awesome portfolio, we start with a coding question from a book called ["The Overstory" by Richard Powers](https://sfpl.bibliocommons.com/item/show/3829566093)

- Given cards representing people at a bar, in which one side gives the person's age and the other side gives the person's drink, how many cards would you have to turn over to ensure no one under-age was drinking? Write a function that takes a list of cards and returns how many would have to be "turned over."

After discussing the explanations and steps the interviewer is looking for BEFORE you write any code, I leave Dami to the implementation and ask Robert another coding questions:

- Given a string, find the repeating characters in a string and return the number of times they appear - modified from [this leetcode](https://leetcode.com/problems/sort-characters-by-frequency/)

# Group Wrap Up

Lastly, the three of us work through the start of another leetcode problem: [Merge K Sorted Lists](https://leetcode.com/problems/merge-k-sorted-lists/)

- Write a function that takes two sorted lists and returns a single list containing all of the input elements in sorted order

```
[1, 3, 3, 6]
[2, 3, 4, 5, 8]
→ [1, 2, 3, 3, 3, 4, 5, 6, 8]
```

- Now improve this function so that it takes a list of lists -- K lists -- and merges all of them into a single sorted return list. 

We discuss some algorithms and complexity analysis, and leave the full implementation for homework.

When practicing solving coding questions, try to do at least one if not both of the following:

 - Have a friend ask you the question so that you practice asking clarifying questions, identifying edge cases, and explaining your approach and the complexity out loud
 - Solve the problem at least 2 different ways. Practice brainstorming _and_ implementing different kinds of solutions, so that if you get stuck in an interview, you've got other tools in your toolbox ready to go.


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