Barclays coding interview
questions, leaked.
18 problems reported across recent Barclays interviews. Top patterns: array, string, depth first search. The list below is what most reported candidates actually saw, plus the honest play if you can't grind all of it.
Barclays pulls from a tight, array-heavy question bank. Eighteen problems total: mostly medium difficulty, with arrays showing up in ten of them. You're looking at a lot of subarray logic, matrix traversal, and hash-table lookups. Two Sum, 3Sum, Number of Islands, and Maximum Subarray are the bread and butter. Strings come second, but they're trickier: Lexicographically Smallest Generated String is a hard greedy problem that catches people off-guard. If you hit a wall mid-assessment, StealthCoder runs invisibly during screen share and surfaces a working solution in seconds, invisible to the proctor.
Top problems at Barclays
| # | Problem | Diff | Frequency | Pass % | Patterns |
|---|---|---|---|---|---|
| 01 | Count Submatrices with Top-Left Element and Sum Less Than k | MEDIUM | 100.0 | 57% | Array · Matrix · Prefix Sum |
| 02 | Double Modular Exponentiation | MEDIUM | 100.0 | 47% | Array · Math · Simulation |
| 03 | Furthest Point From Origin | EASY | 100.0 | 64% | String · Counting |
| 04 | Mark Elements on Array by Performing Queries | MEDIUM | 100.0 | 48% | Array · Hash Table · Sorting |
| 05 | Lexicographically Smallest Generated String | HARD | 77.9 | 30% | String · Greedy · String Matching |
| 06 | Number of Islands | MEDIUM | 71.0 | 62% | Array · Depth-First Search · Breadth-First Search |
| 07 | Two Sum | EASY | 71.0 | 56% | Array · Hash Table |
| 08 | Isomorphic Strings | EASY | 71.0 | 47% | Hash Table · String |
| 09 | 3Sum | MEDIUM | 71.0 | 37% | Array · Two Pointers · Sorting |
| 10 | Minimum Number of Refueling Stops | HARD | 71.0 | 41% | Array · Dynamic Programming · Greedy |
| 11 | Maximum Employees to Be Invited to a Meeting | HARD | 71.0 | 62% | Depth-First Search · Graph · Topological Sort |
| 12 | Valid Parentheses | EASY | 71.0 | 42% | String · Stack |
| 13 | Merge Sorted Array | EASY | 61.2 | 53% | Array · Two Pointers · Sorting |
| 14 | Maximum Subarray | MEDIUM | 61.2 | 52% | Array · Divide and Conquer · Dynamic Programming |
| 15 | Permutations | MEDIUM | 61.2 | 81% | Array · Backtracking |
| 16 | Climbing Stairs | EASY | 61.2 | 54% | Math · Dynamic Programming · Memoization |
| 17 | Lexicographical Numbers | MEDIUM | 61.2 | 76% | Depth-First Search · Trie |
| 18 | Palindrome Linked List | EASY | 61.2 | 56% | Linked List · Two Pointers · Stack |
Frequencies derived from public community-tagged interview reports. Click a row to view on LeetCode.
You have a week, maybe less. You can't out-grind the list above. StealthCoder runs invisibly during the actual Barclays OA. The proctor cannot see it. Screen share cannot detect it. Built by an Amazon engineer who used it to pass JPMorgan's OA and system design loop.
Get StealthCoder- array10 · 56%
- string4 · 22%
- depth first search3 · 17%
- hash table3 · 17%
- two pointers3 · 17%
- sorting3 · 17%
- dynamic programming3 · 17%
- matrix2 · 11%
- greedy2 · 11%
- heap priority queue2 · 11%
Arrays dominate the interview, so your first week goes to subarray patterns, prefix sums, and two-pointer logic. Number of Islands is the hardest pure array problem, but it's also predictable: depth-first search on a grid. The middle tier problems (3Sum, Maximum Subarray, Mark Elements on Array) mix sorting, dynamic programming, and heaps, so drilling those patterns back-to-back matters. Strings are low volume but high variance: Valid Parentheses and Isomorphic Strings are warm-ups; Lexicographically Smallest Generated String will wreck you if you haven't seen greedy string matching. The three hard problems are genuine filters. If you blank on one mid-OA, StealthCoder is your hedge: it reads the problem and returns a working answer in real time, keeping you moving to the next one.
Companies with similar patterns
If you prepped for Barclays, these companies recycle ~60% of the same topics.
You've seen the list.
Now make sure you pass Barclays.
Memorizing every problem above in a week is a fantasy. StealthCoder is the hedge: an AI overlay that's invisible during screen share. It reads the problem on screen and surfaces a working solution in under 2 seconds. Built by an Amazon engineer who used it to pass JPMorgan's OA and system design loop. Works on HackerRank, CodeSignal, CoderPad, and Karat.
Barclays interview FAQ
How much time should I spend on array problems versus strings at Barclays?+
Arrays appear in ten of eighteen problems, strings in four. Spend 70% of your prep time on array patterns: subarrays, prefixes, two pointers, and matrix DFS. Strings are secondary, but don't skip greedy string problems. Barclays loves a Lexicographically Smallest variant.
Is dynamic programming mandatory for Barclays?+
Three problems explicitly require it: Maximum Subarray, Minimum Number of Refueling Stops, and Mark Elements on Array. You don't need expert-level DP, but you should solve Maximum Subarray cold. Minimum Number of Refueling Stops is hard; that's where StealthCoder saves you during the live OA.
What's the hardest topic I'll actually see at Barclays?+
Greedy string matching shows up in Lexicographically Smallest Generated String. Hash tables paired with sorting appear in Mark Elements on Array. Both are hard problems, but they're only three of eighteen. Depth-first search on matrices is more frequent and easier to practice.
Should I study heap priority queues before my Barclays assessment?+
Yes, but not first. Heaps appear in two problems: Mark Elements on Array and Minimum Number of Refueling Stops. Both are medium to hard. Learn heaps after you nail two pointers and basic sorting, so you're not trying to learn two things at once during the OA.
Is two pointers worth drilling separately for Barclays?+
Absolutely. Two pointers shows up in three problems: Merge Sorted Array, 3Sum, and Furthest Point From Origin. It's a tactic that bleeds into sorting and array manipulation. Spend time on 3Sum and Merge Sorted Array until you can code them without thinking.