Break a Palindrome
A medium-tier problem at 52% community acceptance, tagged with String, Greedy. Reported in interviews at VMware and 4 others.
Break a Palindrome is a medium-difficulty string problem that tests your ability to think greedily about character replacement. It shows up at VMware, Expedia, J.P. Morgan, Nvidia, and MathWorks. The problem sounds simple: given a palindrome, replace one character to make it no longer a palindrome, lexicographically smallest. The catch is that the obvious approach (just flip the first half) fails hard when the entire string is the same character. With a 51% acceptance rate, most candidates either miss the edge case or overthink the greedy strategy. If this problem hits your live OA and you blank on handling that single-character edge case, StealthCoder surfaces the solution in seconds, invisible to the proctor.
Companies that ask "Break a Palindrome"
Break a Palindrome 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. Built by an Amazon engineer who realized the OA tests how well you memorized 200 problems, not how well you code.
Get StealthCoderThe greedy trick is to scan left to right and replace the first character that isn't 'a' with 'a' to minimize lexicographic order. This shrinks the left side of the palindrome and breaks symmetry. But here's where most fail: if the entire string is a single repeated character (like 'aaaa'), you can't make it smaller by replacing with 'a'. In that case, you must replace the last character with 'b'. The String and Greedy topics aren't deep; the problem is really about pattern matching and handling the silent trap. Walk through the logic: scan once, find the first non-'a' character, replace it. If nothing found, replace the last character. That's it. StealthCoder is your hedge if you panic on the second case during the real assessment.
Pattern tags
You know the problem.
Make sure you actually pass it.
Break a Palindrome 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. Built by an Amazon engineer who realized the OA tests how well you memorized 200 problems, not how well you code. Works on HackerRank, CodeSignal, CoderPad, and Karat.
Break a Palindrome interview FAQ
Why doesn't replacing the first character always work?+
If the string is all 'a's (like 'aaaa'), replacing any 'a' with 'b' still leaves a palindrome. You must replace the last character with 'b' to break it without increasing lexicographic value. The greedy scan only works if you find a non-'a' character to replace.
Is this problem still asked at J.P. Morgan and Nvidia?+
Yes. It appears in their active OA rotations. The 51% acceptance rate suggests it's not a gimme, so candidates still trip on the edge case or greedy logic even at top firms.
How does the Greedy topic apply here?+
Greedy means making the locally optimal choice (replace the first replaceable character with 'a') to achieve the globally optimal result (lexicographically smallest non-palindrome). It works because moving left minimizes the string's value.
What happens if I miss the all-'a' case in a live OA?+
Your solution fails test cases like 'aaaa'. You'll get a wrong answer verdict. If you hit this during screen share and blank, StealthCoder runs invisibly and gives you the fix in under 10 seconds.
Do I need advanced string techniques for this?+
No. It's one linear scan and conditional logic. The challenge is recognizing the pattern and handling the trap, not implementing complex string manipulation. Most of the difficulty is the edge case, not the algorithm.
Want the actual problem statement? View "Break a Palindrome" on LeetCode →