Interview Hero
Coding round

A mock coding interview where you have to explain yourself.

This mock coding interview works like the real one: a problem, a Python editor, and an interviewer listening while you code. Remy reads each line as you type it, asks what it costs, and runs your tests with you.

25 or 45 minutesPython 3Tests you can run
Start free — 2 practicesSee the questions
What it tests

What a coding interview tests

  • Clarifying before coding

    Restating the problem, asking about input size and edge cases, and saying the approach before the first line.

  • Complexity, out loud

    Naming the time and space cost of your approach, and knowing the cheaper option even if you start with the simple one.

  • Working code, tested

    Code that runs, handles the empty and duplicate cases, and that you can walk through line by line.

  • Recovering when stuck

    Saying where you are stuck and taking a hint well is part of the score, not a failure.

How Remy runs it

She reads your code while you write it.

  1. She reads your editor

    Her questions point at the line you just wrote: "you are sorting every key on line 14 — what does that cost?"

  2. She runs the tests with you

    When you say you are done, you run the tests together and talk through what fails.

  3. One or more problems

    A 25 minute round is one problem. A 45 minute round is two or three, the way many phone screens and onsites run.

From the library

17 coding questions you can practise

Every question in the Interview Hero library for this round, with its level and topics. Pick any of them when you build a round.

Coding

17 questions

  • In-memory rate limiter

    Standardrate limitingsliding windowhash map

  • Min stack

    Warm-upstackmin stackdesign

  • Run-length string compression

    Warm-upstringsrun length encodingtwo pointers

  • Merge intervals

    Warm-upintervalssortinggreedy

  • Two-sum pairs with duplicates

    Standardtwo sumhash maptwo pointers

  • LRU cache

    Standardlru cachehash maplinked list

  • Binary tree level order

    Standardbinary treebfsqueue

  • Log error aggregation

    Standardlogsparsingaggregation

  • Bounded producer-consumer queue

    Hardqueuedequeproducer consumer

  • Most frequent values

    Standardheaptop kcounting

  • Connected components in a graph

    Standardgraphdfsbfs

  • Search a rotated sorted array

    Standardbinary searcharraysrotated array

  • Longest substring without repeats

    Standardsliding windowstringshash map

  • Prefix tree

    Standardtriestringsdesign

  • Fewest coins for an amount

    Standarddynamic programmingcoinsbottom up

  • Shortest word transformation chain

    Hardgraphbfsstrings

  • Minimum edit distance

    Harddynamic programmingstringsedit distance
After the round

Your own words, and what to say next time.

One thing to work onSample report

Say the trade-off before you start coding.

“I'll just use a hash map and sort it, it's probably fine.”11:40 · right before you started typing

Across the round
Try saying

“A heap keeps this at n log k. Sorting everything is simpler — I'll start there and say why it's fine for this input.”

Redo this momentJust this question, one more time
Talk it throughGo over the round with Remy
Went well at 02:05 — you restated the problem
Questions

About the coding round

Can I pick the coding problems?

Yes. When you build a round you can choose problems from the library below, or let us pick them from your job post and level.

Is this like LeetCode?

The problems are the familiar kind, but you are not graded by an online judge. You solve while talking to an interviewer who asks about your choices.

Does Remy give hints?

If you are stuck she nudges you, as a real interviewer would. The report notes where it happened so you can practise that moment.

Keep going

Practice by round

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Try a coding round with Remy.

Your first two practices are free. No card needed.

Start free — 2 practices