Coding Interview Questions I've Been Asked

May 02, 2019

I’m coming towards the end of an interview cycle, and I thought I’d compile the code questions I’ve been asked over the years. At least, the ones I can remember. If and when I find myself interviewing again I’ll update this list.

I’m only including code and code-adjacent questions here, but of course there’s also been a lot of “tell me about a time you had a conflict with a coworker”, “what is your perfect day at work”, and “where do you see yourself in five years” type questions.

These questions are all in JavaScript unless otherwise noted, but I was often given the choice of language.

Esri (2019)

  • What does this code do?:

    (function() {
    	var a = 3;
    	let b = 5;
    	function blah() {
  • Write a function which accepts an array of strings and logs them out in order, with a one-second delay between them. I went over this in more detail in my promise chaining post.

  • Write a function which accepts an array of numbers and filters out the odds

  • Assuming the Array.prototype.filter method doesn’t exist, monkeypatch the Array prototype to create your own version called filt.

  • Write a function which accepts a string and checks if it is a palindrome.

  • What sorts of layout issues might occur when internationalizing an app, and what CSS rules might you apply to mitigate those issues?

SurveyMonkey (2019)

  • Write a function which tells you if a certain search term exists in a given array, assuming that array in unsorted.
  • Write the above function assuming the array is sorted (basically, implement binary search).
  • What happens when you press ‘enter’ in the browser’s address bar?

Mozilla (2019)

Mozilla mostly asked higher-level questions which don’t require coding.

  • What happens when you press ‘enter’ in the address bar?
  • What are some things you might check for if you’re auditing JavaScript code for security?
  • What triggers a DOM repaint?
  • What are the advantages and disadvantages of single page apps versus server-rendered apps.
  • What is undefined in JavaScript?

Periscopic (2017)

  • Implement an algorithm that accepts an array of numeric ranges [start, end] and returns an array where any that are overlapping have been merged. E.g.,

    mergeOverlaps([[1, 3], [5, 7], [9, 11]]); // => [[1,3], [5,7], [9,11]]
    mergeOverlaps([[9, 11], [2, 7], [1, 3]]); // => [9,11], [1,7]]
    mergeOverlaps([[2, 7], [1, 3], [6, 11]]); // => [[1,11]]
  • Describe the algorithm that an elevator uses to decide what floor to go to, assuming there is a single elevator in the building. The interviewer asked specifically about how to prevent “starvation”, where the algorithm might indefinitely ignore a person calling the elevator.

  • Estimate how many delivery drivers FedEx needs to employ to serve the city of Portland.

  • Given a function which draws a line between two points, e.g.,

    drawLine({ from: [x1, y1], to: [x2, y2] });

    Write a function which draws a dashed line between two points, e.g.,

    	from: [x1, y1],
    	to: [x2, y2],
    	dashLength: n,
    	gapLength: m

FocusVision (2015)

I don’t remember much about this interview, except that they asked me to write an entire video upload and encoding application that I spent a huge amount of time on.

  • Using Ruby, write a function which iterates over an array of strings and returns a hash that counts the occurence of each string. The hash should be of the form:

        'hello' => 5,
        'test' => 1,
        'string3' => 6

Dev Bootcamp (2013)

DBC is long-closed, but they did ask one tricky question during the application.

  • Imagine a pair of cubes which sit on your desk and can be rotated to display the current day of the month. These cubes exist in real life. Given that each cube only has six faces, what numbers does each cube need in order to represent every number from 01 to 31?