What are Airbnb coding interview questions?

Airbnb's coding interview questions often focus on testing a candidate's understanding of data structures, algorithms, and real-world problem-solving. The level of difficulty typically ranges from medium to hard, similar to problems found on platforms like LeetCode or HackerRank. Airbnb seeks to assess how efficiently candidates can solve problems while thinking through real-world applications of their solutions.

Here are some examples of coding interview questions commonly asked at Airbnb, along with the main topics they cover:

1. Arrays and Strings

Airbnb often includes problems involving arrays and strings, focusing on manipulation, sorting, or searching techniques.

Example Questions:

• Find All Triplets in an Array that Sum to Zero: Given an array of integers, find all unique triplets that sum up to zero.
• Longest Substring Without Repeating Characters: Given a string, find the length of the longest substring without repeating characters.

Key Concepts: Sliding window, two pointers, sorting.

2. Hash Maps

Airbnb uses hash map-related problems to test a candidate's ability to work with key-value pairs for quick lookup and counting.

Example Questions:

• Two Sum: Given an array of integers, find two numbers such that they add up to a specific target.
• Group Anagrams: Given an array of strings, group the anagrams together.

Key Concepts: Hashing, frequency count, dictionary.

3. Graphs

Graph problems at Airbnb focus on traversal techniques like breadth-first search (BFS) and depth-first search (DFS). These are commonly used for solving problems related to connectivity, shortest path, or exploring structures.

Example Questions:

• Number of Islands: Given a 2D grid where '1' represents land and '0' represents water, count the number of islands.
• Course Schedule: Given a list of prerequisite pairs for courses, determine if you can finish all courses.

Key Concepts: BFS, DFS, topological sort, connected components.

4. Dynamic Programming

Airbnb expects candidates to handle dynamic programming (DP) problems that focus on optimization, recursion, and memoization.

Example Questions:

• Climbing Stairs: You are climbing a staircase. It takes n steps to reach the top. Each time you can either climb 1 or 2 steps. How many distinct ways can you climb to the top?
• Longest Palindromic Substring: Given a string, find the longest substring that is a palindrome.

Key Concepts: Recursion, memoization, bottom-up dynamic programming.

5. Trees and Binary Search Trees (BST)

Questions about binary trees and binary search trees focus on traversal techniques, recursion, and properties of tree structures.

Example Questions:

• Lowest Common Ancestor in a BST: Given a binary search tree (BST), find the lowest common ancestor of two given nodes.
• Binary Tree Maximum Path Sum: Given a binary tree, find the maximum path sum (where the path may or may not include the root node).

Key Concepts: Tree traversal, recursion, backtracking.

6. Backtracking

Backtracking problems involve generating solutions by exploring potential candidates and discarding them if they don’t meet the criteria.

Example Questions:

• N-Queens Problem: Place N queens on an N x N chessboard such that no two queens threaten each other.
• Generate Parentheses: Given n pairs of parentheses, write a function to generate all combinations of well-formed parentheses.

Key Concepts: Recursion, pruning, combinatorics.

7. Sorting and Searching

Sorting and searching questions assess your ability to efficiently process data.

Example Questions:

• Find Kth Largest Element in an Array: Given an array of numbers, find the kth largest element.
• Merge Intervals: Given a collection of intervals, merge overlapping intervals.

Key Concepts: Sorting, divide and conquer, binary search.

8. Real-World Problems

Airbnb also emphasizes problems that simulate real-world applications, such as optimizing or managing large-scale data.

Example Questions:

• Design a Reservation System: Design a system that handles booking and availability of properties, ensuring no double-booking.
• Find the Median from a Data Stream: Maintain a stream of integers and find the median after each new element is added.

9. Linked Lists

Linked list problems typically involve manipulation techniques such as reversing, merging, or detecting cycles.

Example Questions:

• Merge Two Sorted Lists: Merge two sorted linked lists and return it as a single sorted list.
• Detect a Cycle in a Linked List: Determine if a linked list contains a cycle.

10. Recursion

Airbnb might also test your ability to solve recursive problems, which often involve dividing problems into smaller subproblems.

Example Questions:

• Fibonacci Sequence: Calculate the nth Fibonacci number using recursion or dynamic programming.
• Permutations: Generate all possible permutations of a list of numbers.

How to Prepare

To succeed in Airbnb coding interviews, you should focus on:

• Practicing on LeetCode: Focus on medium-to-hard problems, especially in the areas of arrays, graphs, dynamic programming, and trees.
• Using structured learning resources like DesignGurus.io: Courses such as Grokking the Coding Interview can help you develop a solid understanding of common coding patterns and problems.
  • Grokking the Coding Interview

Conclusion

Airbnb’s coding interview questions are designed to assess your problem-solving skills in data structures, algorithms, and real-world applications. Preparing by practicing coding challenges on platforms like LeetCode and focusing on the key areas Airbnb commonly tests will help you perform well during the interview.