Array Questions at Josh Technology: What to Expect

Array questions form the core of Josh Technology's technical assessment, comprising 12 of the 36 total problems. This 1:3 ratio means your performance on array manipulation directly impacts your interview outcome. Arrays are fundamental because they test a candidate's grasp of data organization, in-place algorithms, and efficient traversal—skills essential for backend systems and data processing tasks common at the company. Mastering these questions demonstrates your ability to handle real-world datasets and optimize memory usage, a key priority in their development projects.

What to Expect — Types of Problems

Josh Technology's array problems typically fall into three categories:

1. In-place Modification: Problems requiring you to rearrange, filter, or modify the array without using significant extra space. Examples include moving zeros to the end, removing duplicates from a sorted array, or applying a rotation.
2. Subarray Analysis: Challenges focused on finding contiguous segments that meet specific criteria, such as the maximum sum subarray (Kadane's Algorithm), subarrays with a given sum, or the smallest subarray with a sum greater than a target.
3. Two-Pointer & Sliding Window: Efficient traversal techniques are heavily emphasized. You'll encounter problems involving sorted arrays (like two-sum), window-based calculations, or merging intervals.

Expect constraints that push you towards O(n) time and O(1) space solutions. The problems are designed to weed out brute-force approaches.

How to Prepare — Study Tips with One Code Example

Focus on internalizing patterns, not memorizing solutions. Practice writing code on a whiteboard or plain text editor without autocomplete. For each problem, first clarify edge cases (empty array, single element, negative numbers). Then, verbally explain your logic before coding.

A key pattern is the Two-Pointer Swap for In-place Rearrangement. This is fundamental for problems like segregating even/odd numbers or the classic "Dutch National Flag" (sort colors). The core idea is to use pointers to track positions for swapping elements, achieving O(n) time and O(1) space.

Here is an example of moving all zeros in an array to the end while maintaining the relative order of non-zero elements:

def moveZeros(nums):
    insert_pos = 0
    for num in nums:
        if num != 0:
            nums[insert_pos] = num
            insert_pos += 1
    while insert_pos < len(nums):
        nums[insert_pos] = 0
        insert_pos += 1
    return nums

Recommended Practice Order

Build competence sequentially. Start with basic traversal and building (reverse an array, find min/max). Then master the two-pointer technique on sorted arrays. Next, tackle in-place modification problems (like the zeroes example above). After that, practice sliding window for subarray problems. Finally, combine patterns for more complex challenges like merge intervals or product of array except self. Always analyze the time and space complexity of your final solution.

Practice Array at Josh Technology