Array Questions at Anduril: What to Expect

Array questions make up over half of Anduril's technical interview problem set (25 out of 43 total). This isn't an accident. Anduril builds physical defense technology—autonomous systems, sensor networks, command-and-control software. These systems process massive, real-time streams of spatial data (coordinates, sensor readings, telemetry), which are fundamentally represented and manipulated as arrays. Your ability to efficiently traverse, transform, and reason about this data structure directly reflects your capacity to work on their core engineering challenges. Mastering arrays is non-negotiable for passing their technical screen.

What to Expect — Types of Problems

Anduril's array questions skew toward applied problem-solving rather than abstract computer science. You can expect a heavy emphasis on two-pointer techniques and sliding windows, which are essential for processing sequential data streams. In-place array manipulation is also common, testing your ability to modify data efficiently without extra memory, a key concern in embedded and performance-critical systems. Problems often involve sorting and searching through multidimensional data, simulating real-world tasks like managing drone flight paths or merging sensor feeds. You will rarely see purely academic puzzles; instead, problems are framed around plausible scenarios in robotics, simulation, or data fusion.

How to Prepare — Study Tips with One Code Example

Focus on pattern recognition, not memorization. Drill the core techniques until you can identify and implement them under pressure. For each problem, articulate the why behind your approach—interviewers at Anduril will probe your design choices. Practice writing clean, production-ready code with clear variable names and edge-case handling.

A fundamental pattern is the two-pointer technique for in-place removal. Here is a standard implementation for removing all instances of a specific value from an array in O(n) time and O(1) space.

def remove_element(nums, val):
    # `k` acts as the slow pointer, marking the position for the next valid element.
    k = 0
    for i in range(len(nums)):
        if nums[i] != val:
            nums[k] = nums[i]
            k += 1
    # Elements from index k onward are irrelevant after removal.
    return k

Recommended Practice Order

1. Two-Pointer Fundamentals: Start with basic in-place operations (removal, deduplication) and two-sum variants.
2. Sliding Window: Move to fixed and dynamic window problems, focusing on maximum/minimum subarray and substring problems.
3. Prefix Sum & Hashing: Practice problems involving subarray sums and frequency counting.
4. Simulation & Matrix Traversal: Tackle spiral order, rotation, and other multi-dimensional array manipulations.
5. Anduril-Specific Problems: Finally, work through all 25 array problems tagged for Anduril on CodeJeet to acclimate to their style and difficulty.

Practice Array at Anduril