Best Practices: Coding Questions For Engineers

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1 For Work Best Practices: Coding Questions For Engineers Why Use Coding Questions? 1. Candidates write real working code (and not just pseudocode). 2. Code is evaluated automatically based on test cases of varying difficulty levels. 3. Code is also measured on space and time complexity. 4. You can playback the code to understand the thought process of candidates. 5. Candidates enjoy the overall hiring process while solving a real life challenge. Got a question? support@hackerrank.com 01

2 For Work Creating Coding Questions: 3 Simple Steps 1. Write a problem statement 2. Add code stubs 3. Add test cases 1. PROBLEM STATEMENT Here is a sample Problem Statement. Go through it once. We will refer it throughout this document. Image Problem Description 1. Variable naming convention: a. The variables in the problem statement must match those in the code stubs (to be specified in Step 2). If you refer to a variable in the problem statement as N, it should not be n in the code stubs. b. All variable names, function names etc. should be Italicized, e.g. Notice nonrepeated in the example above (Image 1). Got a question? support@hackerrank.com 02

3 For Work 2. Terminology Usage: A void ambiguity in the problem statement by being as specific as possible e.g. when you want to refer to a binary search tree, do not use tree or binary tree. 1.2 Sample Test Case With Explanation A sample test case, with input and expected output, is strongly recommended to clarify the problem statement to the candidates. This sample test case will be later used in step 3 (Add Test Case) to automate the code evaluation process. 1.3 Constraints Unless you expect candidates to figure out possible constraints of a problem, mention them for clarity. For example, 1. If the code has to read a number as an input, specify the range of that number. This will help candidate decide if int or long int or long long int has to be used. 2. If the input is a string, specify if special characters (like?,. ^%) are also present in the string. You can also specify if it contains consecutive spaces. 2. CODE STUBS 2.1 Set Languages HackerRank supports over 35 programming languages 1. You can choose the set of languages you want to enable for the candidates. 2.2 Add Code Stubs HackerRank helps generate boilerplate code that saves you time while setting up a coding question. This boilerplate code (a.k.a. code stubs) handles input/output in the code. Adding code stubs is strongly recommended as it helps prevent wastage of time for the candidates due to minor errors pertaining to the input/output format. The idea is to let them focus on the algorithm required to solve the problem and not let them worry about the input/output syntax. In the example above (Image 1), code reads a string as input and displays a string as output. So to generate the code stub, you will mention a function name, its input argument and its return type as shown below: 1 Some languages like Go, Groovy, Rust, R, Racket, XQuery, Octave, and Swift can be enabled from backend only. Write a mail to support@hackerrank.com. Got a question? support@hackerrank.com 03

4 For Work Image 2 Once done, click on Generate Code. You will notice a code stub for all the selected languages. Image 2 also shows you code stub generated for Python. 3. TEST CASES Test cases form the basis for automated evaluation of a candidate s code. 3.1 Evaluation A test case consists of an input to the code and an expected output. Once candidates submit the code, it is run against all the test cases. The output from the candidate s code is compared with the expected output to see whether the test case has passed or failed. Image 3 Got a question? support@hackerrank.com 04

5 For Work 3.2 Test Case Basics 1. Sample vs hidden test cases: You can mark a test case as a sample test case. This means that input and expected output are shown to the candidates. For hidden test cases (i.e. ones which are not sample), a candidate will be able to see if the test case passed or not, but will not be able to see the expected output. 2. Score: The overall score for a coding question is the sum of the scores of all the test cases which are successfully passed. You should create test cases of varying difficulty levels and assign points accordingly. This leads to better distinction between outstanding, good and average programmers. 3. Ensure that your input and expected output are in sync with the code stubs you have provided in step 2 (Add Code Stubs) Test Case Pro Tips 1. Use corner test cases e.g. a. a test case where only a single space is present, or b. a test case where only special characters are present in the string 2. You can upload a zip file of all the test cases, especially when input and/or output is too big. The input files in the zip are named input000.txt, input001.txt, & the output files are named output000.txt, output001.txt and so on. 3. Make sure the problem is solvable. Ideally, you should write solution code and check if it works for all the test cases within the specified time limit (see details here). As a rule of thumb, your code should execute in half of the time limit to provide a good buffer When You re Ready to Send a Test Ask the engineers in your team to try the coding question as well. This ensures: 1. Correctness and clarity of the coding question 2. Time provided for the solving the coding question is sufficient 3. Benchmark your internal engineers to your potential hires 2 Check Appendix B for more details Got a question? support@hackerrank.com 05

6 For Work Appendix A: Write Code From Scratch If you expect candidates to be familiar with the handling of input/output, you may choose not to generate any code stubs. Candidates will then have to write full code from scratch. To ensure a smooth candidate experience in this scenario, you will have to clearly specify your input and output format. For the given example: Appendix B: Sync Test Cases With Code Stubs When you are using autogenerated code stubs, ensure that your input and expected output are in sync with the code stubs provided in step 2 (Add Code Stubs). You can refer to the tail portion to understand this. For example: 1. If the input is an array, you will always read in n (denotes array_size) first and then read n array elements in n separate lines. This is required to ensure consistency in reading input across different languages. 2. If the input is a linked list, you will always read in n (denotes the number of elements to be added to the input linked list) and then read n elements in n separate lines. Got a question? support@hackerrank.com 06