Array Questions at Zeta: What to Expect

Array questions dominate Zeta's technical interview, making up 23 of their 35 total problems. This heavy focus signals that Zeta evaluates candidates on foundational data structure manipulation, efficient in-memory computation, and the ability to implement clean, optimal solutions under time constraints. Mastering arrays is non-negotiable for passing their screening.

What to Expect — Types of Problems

Zeta's array problems test core algorithmic patterns. Expect heavy emphasis on:

• Two Pointers & Sliding Window: For problems involving subarrays, pair sums, or removing duplicates. These test your ability to optimize beyond brute-force nested loops.
• In-place Array Manipulation: Tasks like rotating an array, moving zeros, or rearranging elements without using extra space. These assess careful index management and understanding of state.
• Prefix Sum & Hashing: For questions about finding subarrays with a given sum or checking for duplicates. These evaluate your knowledge of time-space trade-offs.
• Simulation & Matrix Traversal: While less frequent, some problems may involve 2D arrays, requiring precise control over row and column indices.

The problems are designed to be solved optimally within a 30-45 minute interview slot, so the most straightforward solution is often insufficient.

How to Prepare — Study Tips with One Code Example

Focus on pattern recognition, not memorization. For each problem type, learn the algorithmic template, then practice variations.

1. Master Fundamentals: Ensure you can implement core operations (iteration, insertion, deletion) and calculate time/space complexity instantly.
2. Pattern-First Approach: Categorize every practice problem. When you see "subarray sum," immediately think "prefix sum or sliding window."
3. Write Clean, Runnable Code: Use descriptive variable names, avoid one-letter indices where unclear, and comment on your logic during interviews.
4. Practice with Constraints: Time yourself. For Zeta, aim for a working, optimal solution in under 20 minutes of coding.

A key pattern is the Two-Pointer Swap for In-place Operations, commonly used to move specific elements (like zeros) to the end.

def move_zeros(nums):
    """Moves all zeros to the end in-place."""
    insert_pos = 0  # Pointer for the next non-zero position

    for i in range(len(nums)):
        if nums[i] != 0:
            nums[insert_pos], nums[i] = nums[i], nums[insert_pos]
            insert_pos += 1
    # All non-zero elements are now in [0:insert_pos], zeros are after.
    return nums

Recommended Practice Order

Tackle problems in this sequence to build competency:

1. Basic Traversal & Operations: Start with problems like removing duplicates or finding a peak element.
2. Two Pointers: Practice pair sums, container with most water, and valid palindrome variations.
3. Sliding Window: Move to fixed or dynamic window problems, such as maximum sum subarray of size K.
4. Prefix Sum & Hashing: Solve subarray sum equals K and two-sum problems.
5. In-place Manipulation: Finally, tackle rotating arrays, moving zeros, and rearrangement problems without extra space.

This progression ensures you layer complexity logically, reinforcing each pattern before combining them.

Practice Array at Zeta