The most-asked coding interview questions, and who asks them
These are the 100 coding questions that appear in the most companies' public interview lists. Each page shows the companies, how often and how recently they are reported, what the question tests and how to practise it.
Which coding interview questions are asked most often?
Two Sum, LRU Cache and Merge Intervals lead the public company-wise lists, each reported by more than 100 companies. The rest of the 100 below are ordered by how many companies report them, and each links to its own page.
How the list is made
We count the companies that report each question in the public company-wise lists and keep the top 100. The lists come from candidate reports, so they show patterns, not guarantees. A question that many companies ask is worth knowing well, but you should still practise the patterns behind it (see the interview-questions pages by topic), because the question you get will often be a variation.
Your first 3 single-question interviews are free for life, every interview report is free, and a new account also gets 6 welcome credits.
The 100 questions
1. Two Sum (Easy): 115 companies, led by Accenture, Adobe and Amazon.
2. LRU Cache (Medium): 109 companies, led by Airwallex, Apple and Aurora.
3. Merge Intervals (Medium): 101 companies, led by Chewy, Grammarly and Grubhub.
4. Valid Parentheses (Easy): 99 companies, led by Bank of America, Chewy and FreshWorks.
5. Longest Substring Without Repeating Characters (Medium): 97 companies, led by FreshWorks, Netskope and Turing.
6. Best Time to Buy and Sell Stock (Easy): 82 companies, led by Millennium, Morgan Stanley and RBC.
7. Number of Islands (Medium): 81 companies, led by Anduril, Hive and Moloco.
8. Group Anagrams (Medium): 79 companies, led by Avito, Disney and Smartsheet.
9. Longest Palindromic Substring (Medium): 74 companies, led by HPE, Nielsen and Cisco.
10. Trapping Rain Water (Hard): 72 companies, led by Cadence, Goldman Sachs and ThousandEyes.
11. Maximum Subarray (Medium): 59 companies, led by Tech Mahindra, Upstart and Target.
12. Container With Most Water (Medium): 54 companies, led by PubMatic, Workday and Wix.
13. Longest Common Prefix (Easy): 52 companies, led by Disney, Revolut and USAA.
14. Rotting Oranges (Medium): 52 companies, led by Informatica, Lyft and ZipRecruiter.
15. Top K Frequent Elements (Medium): 51 companies, led by Chewy, Disney and Pocket Gems.
16. 3Sum (Medium): 49 companies, led by Wissen Technology, Works Applications and Visa.
17. Merge k Sorted Lists (Hard): 49 companies, led by Deloitte, Netskope and X.
18. Search in Rotated Sorted Array (Medium): 49 companies, led by Delhivery, Tinkoff and Walmart Labs.
19. Spiral Matrix (Medium): 49 companies, led by RBC, Zoho and Epic Systems.
20. Sliding Window Maximum (Hard): 47 companies, led by Citadel, LINE and Zenefits.
21. Course Schedule (Medium): 44 companies, led by Nordstrom, Zenefits and Yelp.
22. Median of Two Sorted Arrays (Hard): 44 companies, led by Rippling, Zenefits and Yahoo.
23. Find Median from Data Stream (Hard): 43 companies, led by Cohesity, Tinder and StackAdapt.
24. Koko Eating Bananas (Medium): 43 companies, led by oyo, Trexquant and Zepto.
25. Subarray Sum Equals K (Medium): 43 companies, led by Meta, AMD and Yandex.
26. Kth Largest Element in an Array (Medium): 41 companies, led by Pocket Gems, Avito and Meta.
27. Decode String (Medium): 40 companies, led by Flexport, Tencent and Zoho.
28. Longest Consecutive Sequence (Medium): 40 companies, led by Wissen Technology, Zepto and Okta.
29. Move Zeroes (Easy): 39 companies, led by Chewy, LTI and Sigmoid.
30. Valid Anagram (Easy): 39 companies, led by Nokia, Yelp and American Express.
31. Coin Change (Medium): 38 companies, led by Datadog, Mastercard and Sigmoid.
32. Word Ladder (Hard): 38 companies, led by Navan, Reddit and Yelp.
33. Insert Delete GetRandom O(1) (Medium): 37 companies, led by Affirm, Pocket Gems and SoFi.
34. Letter Combinations of a Phone Number (Medium): 37 companies, led by Dropbox, Trexquant and Epic Systems.
35. Merge Two Sorted Lists (Easy): 37 companies, led by HPE, Wix and Huawei.
36. Min Stack (Medium): 37 companies, led by Paytm, Zenefits and Tinkoff.
37. Sort Colors (Medium): 37 companies, led by Pocket Gems, Slice and Target.
38. String Compression (Medium): 37 companies, led by CrowdStrike, GoDaddy and Yelp.
39. Valid Palindrome (Easy): 37 companies, led by Cadence, Zenefits and LTI.
40. Add Two Numbers (Medium): 36 companies, led by EarnIn, Wix and Adobe.
41. House Robber (Medium): 36 companies, led by CARS24, Cisco and Freecharge.
42. Minimum Window Substring (Hard): 36 companies, led by Wissen Technology, Lyft and Snap.
43. Roman to Integer (Easy): 36 companies, led by AMD, DeltaX and Yahoo.
44. Word Search (Medium): 36 companies, led by Faire, Karat and Uber.
45. Asteroid Collision (Medium): 35 companies, led by Qualtrics, Dream11 and Roku.
46. Climbing Stairs (Easy): 35 companies, led by HPE, Rakuten and Accenture.
47. Course Schedule II (Medium): 35 companies, led by Zenefits, instabase and Snowflake.
48. Generate Parentheses (Medium): 35 companies, led by Zenefits, Walmart Labs and Disney.
49. Product of Array Except Self (Medium): 35 companies, led by ThousandEyes, Asana and ZS Associates.
50. Text Justification (Hard): 35 companies, led by Airbnb, Karat and SIG.
51. Merge Sorted Array (Easy): 34 companies, led by Squarespace, Meta and AMD.
52. Reverse Linked List (Easy): 34 companies, led by Luxoft, Yahoo and Zenefits.
53. Rotate Image (Medium): 34 companies, led by Zillow, Rakuten and SIG.
54. Jump Game (Medium): 33 companies, led by Nielsen, Navi and HashedIn.
55. LFU Cache (Hard): 33 companies, led by Coupang, Netskope and IMC.
56. Time Based Key-Value Store (Medium): 32 companies, led by Axon, Compass and Confluent.
57. Find Peak Element (Medium): 31 companies, led by Urban Company, Meta and Zepto.
58. Next Permutation (Medium): 31 companies, led by PornHub, Meta and Airtel.
59. First Missing Positive (Hard): 30 companies, led by Netskope, MakeMyTrip and ServiceNow.
60. Integer to Roman (Medium): 30 companies, led by X, IBM and Wix.
61. Palindrome Number (Easy): 30 companies, led by Luxoft, Cognizant and Garmin.
62. Best Time to Buy and Sell Stock II (Medium): 29 companies, led by CTC, Careem and Toast.
63. Find First and Last Position of Element in Sorted Array (Medium): 29 companies, led by Instacart, Tinkoff and Splunk.
64. Largest Rectangle in Histogram (Hard): 29 companies, led by thoughtspot, Visa and Coupang.
65. Daily Temperatures (Medium): 28 companies, led by Airwallex, Agoda and Zoho.
66. Longest Increasing Subsequence (Medium): 28 companies, led by Splunk, Samsung and TikTok.
67. Basic Calculator II (Medium): 27 companies, led by Highspot, Rokt and Meta.
68. Gas Station (Medium): 27 companies, led by CME Group, Scale AI and BitGo.
69. Maximal Square (Medium): 27 companies, led by GSA Capital, Wise and DP world.
70. Reverse Nodes in k-Group (Hard): 27 companies, led by Cadence, Qualcomm and Arista Networks.
71. Rotate Array (Medium): 27 companies, led by Fiverr, Box and Apple.
72. Word Break (Medium): 27 companies, led by Pocket Gems, MongoDB and Yahoo.
73. Combination Sum (Medium): 26 companies, led by HPE, Juniper Networks and Snap.
74. Longest Valid Parentheses (Hard): 26 companies, led by Nykaa, Nike and Roku.
75. Reverse Words in a String (Medium): 26 companies, led by Yelp, Snap and Nykaa.
76. Jump Game II (Medium): 25 companies, led by PhonePe, Groupon and HashedIn.
77. Palindromic Substrings (Medium): 25 companies, led by Netskope, Pure Storage and Citadel.
78. Permutations (Medium): 25 companies, led by Workday, Arista Networks and Booking.com.
79. Binary Tree Maximum Path Sum (Hard): 24 companies, led by Baidu, DoorDash and Wix.
80. Happy Number (Easy): 24 companies, led by BlackRock, Nike and Snowflake.
81. Majority Element (Easy): 24 companies, led by Zenefits, Adobe and PornHub.
82. Random Pick with Weight (Medium): 24 companies, led by Two Sigma, Liftoff and Nuro.
83. Valid Sudoku (Medium): 24 companies, led by Confluent, Samsara and Wissen Technology.
84. Edit Distance (Medium): 23 companies, led by Swiggy, Zoho and Cisco.
85. First Unique Character in a String (Easy): 23 companies, led by Goldman Sachs, Morgan Stanley and EPAM Systems.
86. Linked List Cycle (Easy): 23 companies, led by Yahoo, Qualcomm and Nagarro.
87. Remove Duplicates from Sorted Array (Easy): 23 companies, led by Wissen Technology, Bloomberg and Microsoft.
88. Task Scheduler (Medium): 23 companies, led by Roblox, Zeta and Docusign.
89. Basic Calculator (Hard): 22 companies, led by Rokt, Squarepoint Capital and Ripple.
90. Candy (Hard): 22 companies, led by Urban Company, Dropbox and SAP.
91. Design Circular Queue (Medium): 22 companies, led by Cloudflare, Optiver and Splunk.
92. Evaluate Division (Medium): 22 companies, led by Tower Research Capital, Urban Company and DP world.
93. Find the Duplicate Number (Medium): 22 companies, led by Niantic, DP world and Nike.
94. Lowest Common Ancestor of a Binary Tree (Medium): 22 companies, led by Airwallex, Wix and Meta.
95. Maximum Product Subarray (Medium): 22 companies, led by Delhivery, LinkedIn and Adobe.
96. Maximum Profit in Job Scheduling (Hard): 22 companies, led by Pony.ai, Airbnb and Verkada.
97. Reconstruct Itinerary (Hard): 22 companies, led by Pinterest, Netflix and Compass.
98. Regular Expression Matching (Hard): 22 companies, led by Netskope, X and Rokt.
99. Serialize and Deserialize Binary Tree (Hard): 22 companies, led by Yahoo, Hive and Quora.
100. Simplify Path (Medium): 22 companies, led by Patreon, Tinkoff and Meta.
In this section
- Two Sum: which companies ask it and how to practise
- LRU Cache: which companies ask it and how to practise
- Merge Intervals: which companies ask it and how to practise
- Valid Parentheses: which companies ask it and how to practise
- Longest Substring Without Repeating Characters: which companies ask it and how to practise
- Best Time to Buy and Sell Stock: which companies ask it and how to practise
- Number of Islands: which companies ask it and how to practise
- Group Anagrams: which companies ask it and how to practise
- Longest Palindromic Substring: which companies ask it and how to practise
- Trapping Rain Water: which companies ask it and how to practise
- Maximum Subarray: which companies ask it and how to practise
- Container With Most Water: which companies ask it and how to practise
- Longest Common Prefix: which companies ask it and how to practise
- Rotting Oranges: which companies ask it and how to practise
- Top K Frequent Elements: which companies ask it and how to practise
- 3Sum: which companies ask it and how to practise
- Merge k Sorted Lists: which companies ask it and how to practise
- Search in Rotated Sorted Array: which companies ask it and how to practise
- Spiral Matrix: which companies ask it and how to practise
- Sliding Window Maximum: which companies ask it and how to practise
- Course Schedule: which companies ask it and how to practise
- Median of Two Sorted Arrays: which companies ask it and how to practise
- Find Median from Data Stream: which companies ask it and how to practise
- Koko Eating Bananas: which companies ask it and how to practise
- Subarray Sum Equals K: which companies ask it and how to practise
- Kth Largest Element in an Array: which companies ask it and how to practise
- Decode String: which companies ask it and how to practise
- Longest Consecutive Sequence: which companies ask it and how to practise
- Move Zeroes: which companies ask it and how to practise
- Valid Anagram: which companies ask it and how to practise
- Coin Change: which companies ask it and how to practise
- Word Ladder: which companies ask it and how to practise
- Insert Delete GetRandom O(1): which companies ask it and how to practise
- Letter Combinations of a Phone Number: which companies ask it and how to practise
- Merge Two Sorted Lists: which companies ask it and how to practise
- Min Stack: which companies ask it and how to practise
- Sort Colors: which companies ask it and how to practise
- String Compression: which companies ask it and how to practise
- Valid Palindrome: which companies ask it and how to practise
- Add Two Numbers: which companies ask it and how to practise
- House Robber: which companies ask it and how to practise
- Minimum Window Substring: which companies ask it and how to practise
- Roman to Integer: which companies ask it and how to practise
- Word Search: which companies ask it and how to practise
- Asteroid Collision: which companies ask it and how to practise
- Climbing Stairs: which companies ask it and how to practise
- Course Schedule II: which companies ask it and how to practise
- Generate Parentheses: which companies ask it and how to practise
- Product of Array Except Self: which companies ask it and how to practise
- Text Justification: which companies ask it and how to practise
- Merge Sorted Array: which companies ask it and how to practise
- Reverse Linked List: which companies ask it and how to practise
- Rotate Image: which companies ask it and how to practise
- Jump Game: which companies ask it and how to practise
- LFU Cache: which companies ask it and how to practise
- Time Based Key-Value Store: which companies ask it and how to practise
- Find Peak Element: which companies ask it and how to practise
- Next Permutation: which companies ask it and how to practise
- First Missing Positive: which companies ask it and how to practise
- Integer to Roman: which companies ask it and how to practise
- Palindrome Number: which companies ask it and how to practise
- Best Time to Buy and Sell Stock II: which companies ask it and how to practise
- Find First and Last Position of Element in Sorted Array: which companies ask it and how to practise
- Largest Rectangle in Histogram: which companies ask it and how to practise
- Daily Temperatures: which companies ask it and how to practise
- Longest Increasing Subsequence: which companies ask it and how to practise
- Basic Calculator II: which companies ask it and how to practise
- Gas Station: which companies ask it and how to practise
- Maximal Square: which companies ask it and how to practise
- Reverse Nodes in k-Group: which companies ask it and how to practise
- Rotate Array: which companies ask it and how to practise
- Word Break: which companies ask it and how to practise
- Combination Sum: which companies ask it and how to practise
- Longest Valid Parentheses: which companies ask it and how to practise
- Reverse Words in a String: which companies ask it and how to practise
- Jump Game II: which companies ask it and how to practise
- Palindromic Substrings: which companies ask it and how to practise
- Permutations: which companies ask it and how to practise
- Binary Tree Maximum Path Sum: which companies ask it and how to practise
- Happy Number: which companies ask it and how to practise
- Majority Element: which companies ask it and how to practise
- Random Pick with Weight: which companies ask it and how to practise
- Valid Sudoku: which companies ask it and how to practise
- Edit Distance: which companies ask it and how to practise
- First Unique Character in a String: which companies ask it and how to practise
- Linked List Cycle: which companies ask it and how to practise
- Remove Duplicates from Sorted Array: which companies ask it and how to practise
- Task Scheduler: which companies ask it and how to practise
- Basic Calculator: which companies ask it and how to practise
- Candy: which companies ask it and how to practise
- Design Circular Queue: which companies ask it and how to practise
- Evaluate Division: which companies ask it and how to practise
- Find the Duplicate Number: which companies ask it and how to practise
- Lowest Common Ancestor of a Binary Tree: which companies ask it and how to practise
- Maximum Product Subarray: which companies ask it and how to practise
- Maximum Profit in Job Scheduling: which companies ask it and how to practise
- Reconstruct Itinerary: which companies ask it and how to practise
- Regular Expression Matching: which companies ask it and how to practise
- Serialize and Deserialize Binary Tree: which companies ask it and how to practise
- Simplify Path: which companies ask it and how to practise
Frequently asked questions
Where do the company lists come from?
From public lists collected from candidate reports. They are not confirmed by the companies and change over time. This page was last reviewed on 25 October 2026.
Should I just memorise these 100?
No. Learn the patterns behind them and practise explaining your reasoning aloud. Interviewers ask variations, and they judge how you think, not whether you recall an answer.
Sources and review date
Last reviewed 25 October 2026 Statements about other products come from their own public pages:
Keep reading
- Practice interview online, with an interviewer that answers back
- AI mock interview with voice, live coding and a scorecard
- AI interview: what it is and how to prepare for one
- Coding interview practice that includes the interview
- Choosing an interview practice tool
- Company interview guidesRounds and questions by company