Integer to Roman
A medium-tier problem at 69% community acceptance, tagged with Hash Table, Math, String. Reported in interviews at NinjaCart and 35 others.
Integer to Roman shows up across 36 companies, from NinjaCart to Booking.com, and has a 68.6% acceptance rate. That acceptance rate is real, which means 31% of people who attempt this live fail or timeout. The trap is thinking you need some clever math trick. You don't. The problem is a straightforward mapping exercise that becomes trivial once you know the exact pattern. If you blank on the Roman numeral rules during an OA, StealthCoder surfaces a working solution in seconds, invisible to the proctor.
Companies that ask "Integer to Roman"
Integer to Roman is the kind of problem that decides whether you pass. StealthCoder reads the problem on screen and surfaces a working solution in under 2 seconds. Invisible to screen share. The proctor sees nothing. Made by a working Amazon engineer who got tired of watching qualified friends bomb OAs they'd solve cold in an IDE.
Get StealthCoderThe algorithm is simple: build a descending list of integers paired with their Roman symbol equivalents (1000='M', 900='CM', 500='D', etc.), then iterate from largest to smallest, appending symbols and subtracting from the input number. The catch most candidates miss is the subtractive cases: 4 is 'IV' not 'IIII', 9 is 'IX' not 'VIIII'. You must hardcode these in your mapping, or your solution breaks on inputs like 1994. Hash Table and Math aren't the core challenge here. String concatenation and order of traversal are. Common failure: off-by-one logic when decrementing or appending. StealthCoder hedges the live OA when the subtractive rules slip your mind under pressure.
Pattern tags
You know the problem.
Make sure you actually pass it.
Integer to Roman recycles across companies for a reason. It's medium-tier, and most candidates blank under the timer. StealthCoder is the hedge: an AI overlay invisible during screen share. It reads the problem and surfaces a working solution in under 2 seconds. Made by a working Amazon engineer who got tired of watching qualified friends bomb OAs they'd solve cold in an IDE. Works on HackerRank, CodeSignal, CoderPad, and Karat.
Integer to Roman interview FAQ
Why does Integer to Roman have a 31% fail rate if it's marked Medium?+
Most failures come from incomplete subtractive case handling (4, 9, 40, 90, 400, 900). Candidates either omit them or try to derive them algorithmically instead of hardcoding. The logic is simple once you know the pattern, but the pattern itself is brittle.
Is this still asked at Booking.com, Wix, and IBM?+
Yes. All three appear in the top companies list. It's favored by companies that value string manipulation and attention to detail over algorithmic novelty. Expect it in backend and infrastructure roles.
What's the trick to Integer to Roman?+
There is no trick. Hardcode a descending list of 13 integer-symbol pairs (including 900, 400, 90, 40, 9, 4), iterate and append. Candidates who overthink it or try to derive subtractive rules on the fly hit the 31% failure wall.
How does Hash Table relate to this problem?+
You can use a hash map to store the mappings, but it's optional. A simple list of tuples is clearer and avoids hash lookup overhead. Hash Table is listed as a topic because some solutions use it; it's not required.
Can I solve Integer to Roman without hardcoding the subtractive cases?+
Theoretically, no. Roman numerals have hardwired rules for 4, 9, 40, 90, 400, 900. Trying to derive them algorithmically wastes time and introduces bugs. Accept the hardcoding as part of the problem specification.
Want the actual problem statement? View "Integer to Roman" on LeetCode →