Monzo Coding Interview Questions
25 Monzo coding interview problems with full optimal solutions — 14 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 Monzo interviewer values, and a FAQ section.
Showing 14 problems of 25
- #1easyfoundational
1. Two Sum
Given an array of transaction amounts and a target, find two that sum to the target.
- #2easyfoundational
2. Valid Parentheses
Validate that a string of brackets is properly nested and closed.
- #3easyfoundational
3. Merge Two Sorted Lists
Merge two sorted linked lists of transactions into one sorted list.
- #4easyfoundational
4. Remove Duplicates from Sorted Array
Remove duplicate transaction IDs in-place from a sorted array.
- #5easyfoundational
5. Remove Element
Remove all occurrences of a value in-place from an array of transactions.
- #6easyfoundational
6. Search Insert Position
Find the index where a transaction amount should be inserted to keep an array sorted.
- #7easyfoundational
7. Plus One
Add one to a number represented as a digit array (think transaction counter).
- #8easyfoundational
8. Merge Sorted Array
Merge two sorted ledger arrays in-place into the first.
- #9easyfoundational
9. Binary Tree Inorder Traversal
Return the inorder traversal of a tree (useful for sorted category hierarchies).
- #10easyfoundational
10. Single Number
Find the one transaction ID that appears exactly once in a list where every other ID appears twice.
- #11easyfoundational
11. Linked List Cycle
Detect whether a chain of transactions forms a loop, which would corrupt the ledger.
- #12easyfoundational
12. Best Time to Buy and Sell Stock
Given a stream of daily balances on a savings pot, find the maximum profit from one buy and one sell.
- #13easyfoundational
13. Palindrome Number
Decide whether an integer reference number reads the same forward and backward.
- #14easyfoundational
14. Reverse Linked List
Reverse an audit-trail linked list so the most recent ledger entry comes first.