Array Questions at Expedia: What to Expect

Array questions dominate Expedia’s technical interviews, making up 26 of their 54 most frequently asked problems. This isn’t random. Expedia’s core business—searching flights, hotels, and packages—relies heavily on processing and filtering large datasets. Think of user preferences, date ranges, and pricing matrices; these are often modeled and manipulated as arrays or lists. Mastering array algorithms demonstrates you can handle the data transformations and efficient lookups critical to their platforms. If you want to pass their coding screen, array proficiency is non-negotiable.

What to Expect — Types of Problems

Expedia’s array questions tend to focus on practical application over obscure theory. You can expect three main categories:

1. Two-Pointer Techniques: Used for solving problems involving sorted data, palindromes, or finding pairs. This is a staple for optimizing solutions that might otherwise require nested loops.
2. Sliding Window: Prevalent in questions about contiguous subarrays, such as finding the maximum sum of a subarray of size k or the longest substring with distinct characters. This pattern is key for analyzing sequential data.
3. Hash Map for Frequency & Lookup: Many problems involve counting elements, finding duplicates, or checking for the existence of a complement (like two-sum). A hash map (or dictionary) provides constant-time lookups, turning brute-force O(n²) solutions into efficient O(n) ones.

You’ll also encounter transformations like rotations, sorting variations, and basic matrix manipulation. The difficulty often lies in applying the right pattern cleanly under interview pressure.

How to Prepare — Study Tips with One Code Example

Don’t just solve problems—categorize them. For each question you practice, identify the core pattern. Can you solve it with two pointers? Does it need a sliding window? This mental framework is more valuable than memorizing solutions.

Practice writing bug-free code for these patterns from scratch. Here is a fundamental example: the Two-Sum problem, which uses a hash map for efficient lookup. It’s a classic that tests your ability to trade space for time.

def two_sum(nums, target):
    seen = {}
    for i, num in enumerate(nums):
        complement = target - num
        if complement in seen:
            return [seen[complement], i]
        seen[num] = i
    return []

# Example
print(two_sum([2, 7, 11, 15], 9))  # Output: [0, 1]

Recommended Practice Order

Tackle problems in order of foundational concepts to combined patterns:

1. Start with basic traversal and hash map problems (Two-Sum, Contains Duplicate).
2. Move to two-pointer techniques (Valid Palindrome, Two-Sum II on a sorted array).
3. Practice sliding window patterns (Maximum Subarray, Best Time to Buy/Sell Stock).
4. Finally, combine patterns for more complex challenges, like using a hash map within a sliding window.

This builds competence progressively. For Expedia, ensure you can implement each pattern in your chosen language without hesitation.

Practice Array at Expedia