Array Questions at Uber: What to Expect

Why Array Matters at Uber

Uber’s engineering systems handle real-time data at massive scale—tracking driver locations, managing trip routes, processing pricing surges, and optimizing dispatch logic. These operations rely heavily on sequential data structures for efficiency. Arrays provide O(1) access, are cache-friendly, and serve as the foundation for more complex data structures like queues, caches, and adjacency lists. With 212 out of 381 total questions tagged as Array problems, Uber’s interviews consistently test your ability to manipulate indexed data under constraints. Mastering arrays is non-negotiable for roles across backend, mobile, and machine learning platforms.

What to Expect — Types of Problems

Uber’s array questions focus on real-world scenarios. You’ll encounter:

• Sliding Window: For continuous subsequences—think estimating trip durations or analyzing time-series metrics.
• Two Pointers: Common in sorted array problems, such as matching riders to drivers or finding optimal meeting points.
• Prefix Sum: Used for range queries, like calculating total fares over a period or aggregating location densities.
• In-place Manipulation: Rearranging or modifying arrays without extra space, relevant for memory-constrained environments.
• Cyclic Sort: Applied when dealing with permutations or missing/duplicate numbers in a sequence.

Expect follow-ups on time/space complexity trade-offs and scalability. Problems often layer multiple patterns—e.g., combining hash maps with two pointers for subarray sums.

How to Prepare — Study Tips with One Code Example

Focus on pattern recognition, not memorization. Map each problem type to its core technique. Practice explaining your approach aloud, as Uber emphasizes communication. Use constraints to guide your solution—if the array is sorted, consider binary search or two pointers. Always test edge cases: empty arrays, single elements, duplicates.

Here’s a key pattern: Two Pointers for a sorted array problem—finding two numbers that sum to a target.

def two_sum_sorted(nums, target):
    left, right = 0, len(nums) - 1
    while left < right:
        current_sum = nums[left] + nums[right]
        if current_sum == target:
            return [left, right]
        elif current_sum < target:
            left += 1
        else:
            right -= 1
    return []

Recommended Practice Order

Start with fundamentals, then progress to Uber’s frequent patterns:

1. Basic Traversal and Manipulation: Reverse, resize, basic searches.
2. Two Pointers: Pair sums, removing duplicates, merging sorted arrays.
3. Sliding Window: Maximum/minimum subarrays, fixed/variable size windows.
4. Prefix Sum and Hashing: Subarray sum equals K, contiguous sums.
5. In-place Operations: Cyclic sort, Dutch national flag, rotations.
6. Simulation and Matrix Problems: Spiral traversal, rotation (common in location data contexts).

Aim for 15-20 problems per category, prioritizing quality over quantity. Time yourself and simulate interview conditions.

Practice Array at Uber