Backspace String Compare
A easy-tier problem at 49% community acceptance, tagged with Two Pointers, String, Stack. Reported in interviews at Chewy and 11 others.
Backspace String Compare shows up in assessments at Chewy, Roku, Booking.com, and a dozen other companies, yet half the candidates who sit down with it blank on the approach. You've got two strings, both with backspace characters, and you need to figure out if they're equal after all the backspaces resolve. The trap is trying to simulate it naively. The trick is knowing which direction to iterate and what two pointers actually lets you skip building the resolved strings. If this problem hits your live assessment and you freeze on the pattern, StealthCoder solves it in seconds invisible to the proctor.
Companies that ask "Backspace String Compare"
Backspace String Compare 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 for the engineer who has done the work but might still blank with a webcam pointed at him.
Get StealthCoderThe naive instinct is to build out both final strings by processing each backspace, then compare them. That works, but it burns space and time. The real pattern is two pointers walking backward from the end of each string simultaneously, skipping characters based on backspace count as you go. When you encounter a '#', you increment a backspace counter and move left. When the counter is zero, you compare characters. If they don't match, the strings aren't equal. If one string runs out before the other (after accounting for backspaces), they're unequal. Two Pointers, String, and Simulation all apply because you're literally simulating the backspace process by walking backward. Most people overthink it or implement it forward and get the logic tangled. StealthCoder is your hedge if you walk into the live OA unprepared on this specific variant.
Pattern tags
You know the problem.
Make sure you actually pass it.
Backspace String Compare recycles across companies for a reason. It's easy-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 for the engineer who has done the work but might still blank with a webcam pointed at him. Works on HackerRank, CodeSignal, CoderPad, and Karat.
Backspace String Compare interview FAQ
Is this problem actually asked by real companies?+
Yes. Chewy, Roku, Booking.com, Grammarly, Wayfair, IBM, and several others have reported asking it. It's not a rare edge case. The acceptance rate hovers around 49 percent, which means a meaningful chunk of candidates either misread the problem or fumble the implementation.
Why doesn't building both strings work?+
It does work, but it's O(n + m) space and O(n + m) time to build, then O(n + m) to compare. Two pointers is O(n + m) time with O(1) space. In an online assessment, interviewers prefer the space-optimal approach. It's also the intended insight.
What's the trick I always miss?+
Walking backward instead of forward. When you go backward, you see the net effect of backspaces as you move left. Going forward gets messy because you don't know yet how many backspaces will affect a character. Backward, the backspace logic is local and clean.
How does Two Pointers connect to this problem?+
You maintain one pointer per string, both starting at the end. They move left in sync, skipping invalid characters (those deleted by backspace). When both pointers land on a valid character, you compare. If they diverge, the strings aren't equal.
Will I see this on the harder problems list?+
No. It's marked EASY, and the acceptance rate reflects that. If you're prepping for a FAANG or startup assessment, this is a warmup or a filter. Don't blank on it. It's the kind of problem where a correct, clean solution takes two minutes and signals you're serious.
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