Coding.
First Missing Positive Test
The "First Missing Positive" challenge is a classic algorithmic problem used to assess a candidate's ability to design efficient solutions under strict time and space constraints. It tests their understanding of array manipulation, in-place algorithm
Summarize this test and see how it helps assess top talent with:
- Test type
- Coding
- Duration
- 29 min
- Level
- Advanced
- Questions
- 1
Skills measured
Array
Hash Table
Use of the First Missing Positive Test
You are given an unsorted integer array nums. Your task is to find the smallest positive integer that does not appear in the array.
- Your solution must run in O(n) time.
- It must use O(1) auxiliary space (excluding the input).
This problem requires thoughtful use of indexing and in-place data rearrangement to track existing positive integers efficiently.
Who is this test for?
This problem is particularly relevant for assessing candidates for software development roles that involve:
Algorithm design
Space/time optimization
Systematic debugging and edge case handling
It appears frequently in technical interviews because of its deceptively simple description and the optimal O(n) solution's complexity. Solving it demonstrates deep knowledge of array manipulation, in-place transformations, and the ability to write clean, performant code under constraints.
Hire Better. Faster. Globally.
Testlify helps you find the best talent anywhere in the world with a smooth and simple hiring experience.
Candidate satisfaction
Recruiter efficiency
Decrease in time to hire
The First Missing Positive Subject Matter Expert
Testlify's skill tests are designed by experienced SMEs (subject matter experts). We evaluate these experts based on specific metrics such as expertise, capability, and their market reputation. Prior to being published, each skill test is peer-reviewed by other experts and then calibrated based on insights derived from a significant number of test-takers who are well-versed in that skill area. Our inherent feedback systems and built-in algorithms enable our SMEs to refine our tests continually.
Why Testlify.
Why choose Testlify
Elevate your recruitment process with Testlify, the finest talent assessment tool. With a diverse test library boasting 3500+ tests, and features such as custom questions, typing test, live coding challenges, Google Suite questions, and psychometric tests, finding the perfect candidate is effortless. Enjoy seamless ATS integrations, white-label features, and multilingual support, all in one platform. Simplify candidate skill evaluation and make informed hiring decisions with Testlify.
Related tests
Node.js
Node.js Test is a technical assessment used by hiring managers and recruiters to evaluate a candidate's Node.js development proficiency. It includes various question types and practical tasks to meas…
JavaScript (Coding): Intermediate Level Algorithms
The JavaScript (Coding): Intermediate Level Algorithms evaluates a candidate’s ability to program a small algorithm in JavaScript, testing their basic programming skills.
HTML5
This test evaluates a candidate's capacity to use the best practices based on HTML 5. This test helps identify candidates with practical experience using HTML tags and characteristics, such as tables…
Sample reports
SMART
View report16 Personality trait
View reportBig Five Inventory (BFI)
View reportBig Five Personality
View reportCulture Fit
View reportDISC Personality
View reportEnneagram Personality
View reportLeadership Style
View reportMotivational Traits
View reportSales Profiler
View reportSelf Esteem
View reportTop five hard skills interview questions for First Missing Positive
Here are the top five hard-skill interview questions tailored specifically for First Missing Positive. These questions are designed to assess candidates’ expertise and suitability for the role, along with skill assessments.
Frequently asked questions (FAQs) for First Missing Positive Test
Can't find the test you need?
Request a custom assessment and our subject-matter experts will build it for your role — peer-reviewed and validated before it ships.