Udemy Coding Interview Questions
26 Udemy coding interview problems with full optimal solutions — 15 easy, 8 medium, 3 hard. Every problem ships with multiple approaches (brute-force first, then the optimal), complexity tables for each, company-specific tips on what an Udemy interviewer values, and a FAQ section.
- #1easyfoundational
1. Two Sum
Find two indices that sum to a target — Udemy's warm-up hash-map check before deeper course-search or payment questions.
- #2easyfoundational
2. Valid Parentheses
Validate that brackets nest correctly — a stack warm-up Udemy uses to gauge whether you reach for the right data structure before the harder DRM/search rounds.
- #3easyfoundational
3. Merge Two Sorted Lists
Merge two sorted linked lists into one sorted list — Udemy uses this to test pointer hygiene before deeper recommendation-feed merge questions.
- #4easyfoundational
4. Remove Duplicates from Sorted Array
Dedupe a sorted array in place — Udemy uses this to gauge two-pointer hygiene before dedupe questions on course catalog imports.
- #5easyfoundational
5. Remove Element
Strip occurrences of a value in place — Udemy uses this to test pointer mechanics before harder catalog-cleanup problems.
- #6easyfoundational
6. Search Insert Position
Find the index of a target or where it would insert — Udemy's classic binary-search check before course-catalog lookup questions.
- #7easyfoundational
7. Maximum Subarray
Find the contiguous subarray with the largest sum — Udemy uses Kadane to test whether you can recognize a DP pattern in a casual array problem.
- #8easyfoundational
8. Plus One
Increment a big integer represented as a digit array — Udemy uses this to test carry handling before deeper payment-amount math problems.
- #9easyfoundational
9. Merge Sorted Array
Merge two sorted arrays into the first in place — Udemy uses this to test reverse-pointer thinking before merging course-result feeds.
- #10easyfoundational
10. Binary Tree Inorder Traversal
Walk a binary tree in inorder — Udemy uses this as a stack-recursion warm-up before harder course-category tree problems.
- #11easyfoundational
11. Same Tree
Decide whether two binary trees are structurally and value-equal — Udemy uses this to test recursive equality before harder course-tree diff problems.
- #12easyfoundational
12. Symmetric Tree
Check whether a binary tree is a mirror of itself — a Udemy warm-up that tests recursive thinking around tree structure.
- #13easyfoundational
13. Maximum Depth of Binary Tree
Find the maximum depth of a binary tree — Udemy uses this to probe recursive DFS fundamentals before asking about course-category tree traversals.
- #14easyfoundational
14. Balanced Binary Tree
Determine if a binary tree is height-balanced — Udemy uses this to test whether candidates can avoid redundant tree traversals with a bottom-up approach.
- #15easyfoundational
15. Path Sum
Check if a root-to-leaf path sums to a target — Udemy uses this as a gateway to harder path-aggregation problems in recommendation scoring.
- #16mediumfoundational
16. Add Two Numbers
Sum two numbers represented as reversed linked lists — Udemy uses this to probe carry propagation logic common in payment and pricing calculations.
- #17mediumfoundational
17. Longest Substring Without Repeating Characters
Find the length of the longest substring without repeating characters — Udemy applies the sliding-window pattern to course-title deduplication and content search.
- #18mediumfoundational
18. Longest Palindromic Substring
Find the longest palindromic substring — Udemy uses expand-around-center to evaluate string manipulation instincts for search autocomplete features.
- #19mediumfoundational
19. Container With Most Water
Maximize the area between two height lines using two pointers — Udemy uses this to evaluate greedy intuition for capacity-planning and bandwidth-allocation problems.
- #20mediumfoundational
20. 3Sum
Find all unique triplets that sum to zero — Udemy uses this to test deduplication logic relevant to course bundle pricing and recommendation filtering.
- #21mediumfoundational
21. Letter Combinations of a Phone Number
Generate all letter combinations from phone-pad digits — Udemy uses this backtracking warm-up before harder search autocomplete and tag-generation problems.
- #22mediumfoundational
22. Search in Rotated Sorted Array
Binary search in a rotated sorted array — Udemy uses this to evaluate whether candidates can adapt standard binary search for marketplace catalog lookups with shifted indices.
- #23mediumfoundational
23. Coin Change
Find the fewest coins needed to make a target amount — Udemy uses bottom-up DP here to evaluate dynamic-programming fundamentals for coupon and discount optimization problems.
- #24hardfoundational
24. Median of Two Sorted Arrays
Find the median of two sorted arrays in O(log(m+n)) — Udemy uses this to test binary search mastery applied to statistical ranking and recommendation scoring.
- #25hardfoundational
25. Regular Expression Matching
Implement regex matching with '.' and '*' — Udemy uses 2D DP here to assess dynamic programming depth in candidates targeting search and content filtering roles.
- #26hardfoundational
26. Trapping Rain Water
Compute how much water is trapped between elevation bars — Udemy uses this two-pointer classic to test candidates' ability to reason about prefix/suffix max arrays for data-bucketing problems.