Top Meta (Facebook) DSA Interview Questions and How to Prepare

Top Meta DSA Questions by Category

Array and String Questions

1. Rotate a matrix by 90 degrees (Hard)
   • Hint: Use layer-by-layer rotation.
2. Minimum window substring (Medium)
   • Expected Time: O(n) with sliding window.

Tree and Graph Questions

1. Clone a connected undirected graph (Medium)
   • Use BFS and hashing for node mapping.
2. Validate BST (Easy)
   • Track min/max bounds recursively.

Comparison of Key Meta DSA Question Types

Top Meta DSA Questions 

Array and String Questions 

1. Trapping Rain Water (Hard)

Problem: Calculate how much rainwater can be trapped between bars given an elevation map.
Approach: Use a two-pointer technique to track left/right max heights.
Time Complexity: O(n)
Meta-Specific Tip: This problem mirrors optimizing data storage for user-generated content (e.g., Instagram Stories).

2. Product of Array Except Self (Medium)

Problem: Return an array where each element equals the product of all other elements except itself.
Approach: Use prefix and suffix product arrays without division.
Time Complexity: O(n)
Meta-Specific Tip: Used in ad-targeting algorithms to compute user interest scores.

3. Longest Palindromic Substring (Medium)

Problem: Find the longest palindrome in a string.
Approach: Expand around center or use dynamic programming.
Time Complexity: O(n²)
Meta-Specific Tip: Relevant for detecting hate speech or spam in comments.

4. Valid Parentheses (Easy)

Problem: Check if a string of brackets is valid.
Approach: Use a stack to track opening brackets.
Time Complexity: O(n)
Meta-Specific Tip: Meta tests this to evaluate code quality for UI components.

Tree and Graph Questions 

5. Serialize and Deserialize a Binary Tree (Hard)

Problem: Convert a binary tree to a string and reconstruct it.
Approach: Use BFS or preorder traversal with markers.
Time Complexity: O(n)
Meta-Specific Tip: Critical for storing hierarchical data (e.g., Facebook Groups).

6. Lowest Common Ancestor in a BST (Medium)

Problem: Find the LCA of two nodes in a binary search tree.
Approach: Traverse the tree using BST properties.
Time Complexity: O(h)
Meta-Specific Tip: Used in privacy settings to find shared user permissions.

7. Number of Islands (Medium)

Problem: Count islands in a 2D grid.
Approach: DFS/BFS to mark visited land cells.
Time Complexity: O(mn)
Meta-Specific Tip: Models social network connectivity (e.g., friend clusters).

8. Clone Graph (Medium)

Problem: Create a deep copy of a connected undirected graph.
Approach: BFS with a hashmap to track cloned nodes.
Time Complexity: O(n)
Meta-Specific Tip: Reflects how Meta duplicates user profiles for testing.

Dynamic Programming Questions 

9. Coin Change (Medium)

Problem: Find the minimum coins needed to make an amount.
Approach: Bottom-up DP with a 1D array.
Time Complexity: O(amount * coins)
Meta-Specific Tip: Used in ad billing systems to optimize payment methods.

10. Longest Increasing Subsequence (Medium)

Problem: Find the length of the longest subsequence where elements are sorted.
Approach: Patience sorting or binary search.
Time Complexity: O(n log n)
Meta-Specific Tip: Helps rank news feed content by engagement trends.

Practice Tip: For hands-on coding practice with these questions, enroll in the DSA Mastery Course to access 100+ mock problems and detailed solutions.

How to Prepare Effectively

Step 1: Build Strong Fundamentals

• Solve 50+ LeetCode problems (Meta’s question bank overlaps 60% with LeetCode).
• Study Top 10 Greedy Algorithms.

Step 2: Mock Interviews

Platforms like Pramp simulate Meta’s interview environment. Aim for 20+ mock sessions.

Step 3: Optimize Time Management

• Allocate 10 minutes for problem analysis, 25 for coding, and 5 for testing.