N26 Coding Interview Questions
25 N26 coding interview problems with full optimal solutions — 13 easy, 9 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 N26 interviewer values, and a FAQ section.
Showing 13 problems of 25
- #1easyfoundational
1. Two Sum
Given an array of integers and a target, return indices of the two numbers that add up to the target. N26 uses this as a warm-up to gauge hash-map fluency before deeper transaction-matching questions.
- #2easyfoundational
2. Valid Parentheses
Validate whether a string of brackets is balanced using a stack. N26 frames this as a sanity check before deeper questions about bracket-style transaction grouping.
- #3easyfoundational
3. Merge Two Sorted Lists
Merge two sorted linked lists into one sorted list. N26 uses this to probe pointer hygiene before scaling up to merging chronologically sorted multi-currency transaction streams.
- #4easyfoundational
4. Remove Duplicates from Sorted Array
Remove duplicates in-place from a sorted array and return the new length. N26 uses this for collapsing repeated transactions returned by upstream ledgers.
- #5easyfoundational
5. Remove Element
Remove all instances of a given value from an array in-place. N26 reframes this as filtering reversed transactions out of a daily settlement batch.
- #6easyfoundational
6. Search Insert Position
Find the index where a target would be inserted to keep a sorted array sorted. N26 uses this to confirm binary-search comfort before moving to time-ordered transaction lookups.
- #7easyfoundational
7. Plus One
Increment a number represented as a digit array. N26 uses this to surface carry-handling intuition, a precursor to integer-cents arithmetic for monetary amounts.
- #8easyfoundational
8. Merge Sorted Array
Merge two sorted arrays in-place into the first. N26 frames this as merging a new batch of cleared transactions into the running balance log.
- #9easyfoundational
9. Single Number
Given a non-empty array where every element appears twice except for one, find the single one. N26 uses this to test bitwise fluency before deeper ledger-reconciliation problems where one unmatched debit needs to be isolated.
- #10easyfoundational
10. Majority Element
Find the element that appears more than n/2 times in an array. N26 frames this as detecting the dominant currency in a multi-currency batch.
- #11easyfoundational
11. Happy Number
Determine if a number eventually reaches 1 when repeatedly replaced by the sum of squares of its digits. N26 uses it to gauge cycle-detection instinct before harder ACH retry-loop questions.
- #12easyfoundational
12. Isomorphic Strings
Decide whether two strings are isomorphic - characters in one map one-to-one to characters in the other. N26 uses this as a stand-in for column-mapping checks in their KYC field normalization pipeline.
- #13easyfoundational
13. Contains Duplicate
Return true if any value appears at least twice in the array. N26 uses this as the simplest version of their idempotency-key duplicate-detection check.