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Barclays DSA Interview Questions

Gearing up for a Barclays Technology Analyst or Software Engineer interview in 2026? This DSA sheet is mapped to what Barclays actually tests in its coding rounds and technical interviews — a solid mix of arrays, strings, and hash-based problems, linked list and tree fundamentals, and OOP-heavy design questions inspired by real banking systems like account ledgers, transaction processing, and order matching. Barclays interviews typically move through 2-3 problems per round, rewarding candidates who write clean, correct code quickly and can reason confidently about time and space complexity. This sheet compiles 57 of the most frequently reported Barclays interview questions sourced from LeetCode and GeeksforGeeks, tagged by topic, difficulty, and candidate-reported popularity — so you prepare with focus instead of guesswork.

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1. Two Sum
LeetCode•
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Very Hot
2. Valid Parentheses
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Hot
3. Best Time to Buy and Sell Stock
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Very Hot
4. Best Time to Buy and Sell Stock II
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Hot
5. Maximum Subarray
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Hot
6. Merge Intervals
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Hot
7. Meeting Rooms II
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Hot
8. Group Anagrams
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Warm
9. Product of Array Except Self
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Warm
10. Subarray Sum Equals K
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Hot
11. 3Sum
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Warm
12. Container With Most Water
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Warm
13. Search in Rotated Sorted Array
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Hot
14. Kth Largest Element in an Array
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Warm
15. Top K Frequent Elements
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Warm
16. Longest Substring Without Repeating Characters
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Hot
17. Valid Anagram
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Warm
18. Reverse Linked List
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Hot
19. Merge Two Sorted Lists
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Warm
20. Linked List Cycle
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Warm
21. Add Two Numbers
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Warm
22. LRU Cache
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Very Hot
23. Binary Tree Level Order Traversal
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Hot
24. Validate Binary Search Tree
LeetCode•
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Hot
25. Lowest Common Ancestor of a Binary Tree
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Warm
26. Maximum Depth of Binary Tree
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Warm
27. Diameter of Binary Tree
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Warm
28. Number of Islands
LeetCode•
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Warm
29. Course Schedule
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Warm
30. Accounts Merge
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Warm
31. Word Break
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Warm
32. Coin Change
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Warm
33. House Robber
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Warm
34. Climbing Stairs
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Warm
35. Longest Increasing Subsequence
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Warm
36. Edit Distance
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Warm
37. Word Search
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Warm
38. Subsets
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Warm
39. Permutations
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Warm
40. Implement Queue using Stacks
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Warm
41. Min Stack
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Hot
42. Evaluate Reverse Polish Notation
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Warm
43. Design Twitter
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Warm
44. Insert Delete GetRandom O(1)
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Warm
45. Spiral Matrix
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Warm
46. Rotate Image
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Warm
47. Design an ATM Machine
GeeksforGeeks•
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Hot
48. Design a Bank Account Management System
GeeksforGeeks•
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Hot
49. Design a Stock Order Book System
GeeksforGeeks•
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Hot
50. Detect Cycle in a Directed Graph
GeeksforGeeks•
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Warm
51. Dijkstra's Shortest Path Algorithm
GeeksforGeeks•
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Warm
52. Longest Common Subsequence
GeeksforGeeks•
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Warm
53. Find the Kth Smallest Element in an Unsorted Array
GeeksforGeeks•
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Warm
54. Job Sequencing Problem
GeeksforGeeks•
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Warm
55. Rat in a Maze Problem
GeeksforGeeks•
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Warm
56. OOP Concepts - Inheritance and Polymorphism
GeeksforGeeks•
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Hot
57. Boundary Traversal of a Binary Tree
GeeksforGeeks•
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Warm