LeetCode Question · Jul 2022 · Los Angeles

Atlassian | OA | MEX Problem

SWE OA

5 upvotes 1,395 views 3 replies

Question Details

Question: MEX Problem Given an array arr contalning n non-negative integers and an element x, in one operation, x can be added to or subtracted from any element of the array. MEX...

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Question:
MEX Problem
Given an array arr contalning n non-negative integers and an element x, in one operation, x can be added to or subtracted from any element of the array. MEX of an array is defined as the smallest non-negative integer which is not present in the array. For example, the MEX of [0, 1, 1, 3] is 2, and the MEX of [1, 2, 4] is 0.
Find the maximum possible MEX of the array that can be achieved by doing the above operation any number of times.

The question has been solved, Thanks @anarchaworld

I got this question in the Atlassian Coding Test but was unable to solve the question attached below.

Solution:

private int solve(int[] A, int X){
 int[] reminder = new int[X];
 for (int n : A){
 reminder[n%X]++;
 }
 for (int i = 0; i < A.length; i++){
 if (--reminder[i%X]<0){

**return** i;
 }
 }

**return** A.length;
}

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About This Question

This is a reported interview question from a atlassian interview for a swe role during the oa round reported in 2022.

It covers the following topics: Arrays .

Topics

Arrays

About Atlassian Interview Reports

This question was reported by a candidate who interviewed at Atlassian. LeakCode aggregates interview reports from 10+ sources, including 1Point3Acres, Glassdoor, LeetCode Discuss, Blind, Reddit, Indeed, and Nowcoder. Each report is translated where necessary, deduplicated against existing entries, and tagged by company, role, round type, and reporting date.

Use this question as one calibration data point, not a memorization target. Companies typically rotate their question pools every 2-4 months; the exact wording of a 2024 question may differ from what you encounter today. The underlying pattern, difficulty level, and follow-up depth at Atlassian are the higher-signal extractions to take from this report.

For broader preparation context, the Atlassian interview process typically includes a recruiter screen, one or two technical phone screens, and a 4-5 round on-site loop covering coding, system design (at L4+ levels), and behavioral. Reports tagged on LeakCode show the round-by-round distribution and typical difficulty calibration. To browse questions filtered by round type and seniority, use the company hub linked above.

How To Practice This Type of Question

Solve similar problems on LeetCode under timed conditions (25-35 minutes per medium difficulty). The goal is pattern recognition: recognize the underlying technique (sliding window, two-pointer, BFS, memoized recursion, etc.) within 60-90 seconds of reading. Strong candidates verbalize their hypothesis out loud before coding, then iterate based on feedback. Weak candidates dive into implementation immediately, lose time on the wrong approach, and run out of time for follow-ups.

Companies update their question pools every 2-4 months. The exact wording of any given question may have been retired by the time you interview. Focus your prep on the pattern, not the specific problem. The patterns that appear in Atlassian reports consistently are the ones worth investing in; one-off niche problems are not.

During Your Atlassian Round

Apply the standard interview round template: clarify requirements (2-3 minutes), state your approach out loud and confirm direction with the interviewer (3-5 minutes), code with narration (15-25 minutes), test with concrete examples including edge cases (5 minutes), discuss optimization or trade-offs if time permits (5 minutes). This template is universally accepted across FAANG and adjacent companies; deviating from it produces weaker interviewer feedback signal.

The single most predictive failure mode in Atlassian reports tagged "no hire": not asking clarifying questions. Interviewers are explicitly trained to weight this. Strong candidates ask 3-5 clarifying questions even on problems that look obvious; weak candidates dive into code immediately. The clarifying-question check is often the first signal recorded in the interviewer's written notes.