Masking Personal Information
A medium-tier problem at 51% community acceptance, tagged with String. Reported in interviews at X and 0 others.
String manipulation problems look easy until the rules get strict. Masking Personal Information is a medium-difficulty problem that tests whether you can iterate through a string, identify patterns, and surgically replace characters without breaking the underlying structure. X has asked this one. It's not a haul-the-entire-tree problem, but it's exactly the kind of task where you either nail it cleanly or spend ten minutes debugging edge cases in your live assessment. If this problem surfaces during your OA and the masking logic trips you up, StealthCoder surfaces a working solution in seconds, invisible to the proctor.
Companies that ask "Masking Personal Information"
Masking Personal Information 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 trick here isn't algorithmic complexity. It's parsing rules. You get a string (email, phone, or IP) and need to mask specific characters while keeping anchors visible. The naive approach is string concatenation in a loop, which works but leaves you vulnerable to off-by-one errors on the boundary indices. The real pattern: identify input type, determine which positions to mask, and build the output safely. Common failure: assuming all three input types follow the same masking logic. They don't. Email masks the middle substring, phone masks the middle four digits, IP masks certain octets. You need a branching handler for each. StealthCoder is the hedge when you freeze on the exact masking rules during screen share.
Pattern tags
You know the problem.
Make sure you actually pass it.
Masking Personal Information 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.
Masking Personal Information interview FAQ
How hard is Masking Personal Information really?+
Medium difficulty with a 50% acceptance rate. It's not a tree traversal or graph problem. The challenge is parsing rules correctly and avoiding index mistakes. If you've built string validators before, the logic feels familiar. The difficulty comes from precision, not complexity.
Is this still asked at companies like X?+
X has reported it. String problems cycle through interviews at most mid-to-large companies. Acceptance data suggests it's not rare. It's the kind of problem that doesn't require advanced data structures, so interviewers use it to filter for clean code and attention to detail.
What's the trick to avoiding off-by-one errors?+
Work backwards from the end indices. If you're masking positions 3 to 7, clarify whether 7 is inclusive or exclusive before you write a single line. Then test your substring boundaries with a short example by hand. Many failures happen because candidates guess at boundary logic instead of verifying.
Do I need regex for this?+
Not required. Regex can validate input type, but the masking itself is cleaner with string slicing and concatenation. Most solutions use simple character checks (is it '@' or '-') to identify type, then index-based masking. Keep it readable over clever.
How does this relate to string topics more broadly?+
It's pure string manipulation: slicing, concatenation, character iteration. No hash maps, no sorting. It tests whether you can handle positional logic on immutable strings without creating garbage in memory. Solid practice for any string-focused round.
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