Get Equal Substrings Within Budget
A medium-tier problem at 59% community acceptance, tagged with String, Binary Search, Sliding Window. Reported in interviews at IBM and 0 others.
Get Equal Substrings Within Budget is a medium-difficulty sliding window problem that looks deceptively simple until you realize the trap: most candidates try to brute force every substring comparison and run out of time. The problem asks you to find the longest substring where the cost of converting characters equals some budget, and the naive approach dies on larger inputs. IBM has asked this one. The trick is recognizing that this is a constrained window problem, not a substring search problem. If you freeze on this during your live assessment, StealthCoder solves it in seconds, invisible to the proctor.
Companies that ask "Get Equal Substrings Within Budget"
Get Equal Substrings Within Budget 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 core pattern is sliding window with a cost accumulator. You maintain a window and expand it character by character, tracking the sum of absolute differences between the source and target strings. When the cost exceeds your budget, you shrink from the left. The real insight is that once you shrink, you don't need to reset. This is where candidates get stuck: they either re-scan the window each iteration (O(n squared) death spiral) or overthink a binary search variation when the single-pass window is already optimal. Common pitfall: tracking the wrong variable or forgetting to update your maximum length answer when you shrink. If the problem hits your live OA cold, you need the window mechanics to be automatic. StealthCoder surfaces the complete solution immediately so you're not debugging under time pressure.
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Get Equal Substrings Within Budget 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.
Get Equal Substrings Within Budget interview FAQ
Is this really a sliding window problem or do I need binary search?+
Pure sliding window. Binary search is optional overkill here. The two-pointer window expands right and contracts left as cost exceeds budget, giving you O(n) time. Many candidates overthink it because the problem mentions budget, but the window is the clean path. The input topics list sliding window first for a reason.
What's the acceptance rate and am I supposed to get this right?+
Acceptance sits around 59 percent, so it's solidly medium. You're not expected to nail it cold. The problem tests whether you recognize the sliding window pattern fast, not whether you're a genius. Most misses come from implementation bugs, not algorithmic confusion.
How does this relate to prefix sum, which is listed as a topic?+
Prefix sum is optional here. Some solutions precompute costs to avoid recalculating inside the window loop, but it's not required for O(n) time. If you use prefix sum, it's a micro-optimization. The core algorithm is window-based, not prefix-based.
What's the common mistake that kills the time limit?+
Recalculating substring costs or window cost from scratch after each pointer move. That's O(n squared) and timeouts on large inputs. You must update cost incrementally: add one character when expanding, subtract when shrinking. One pass, one accumulator.
IBM asked this. Is it a gate or a warm-up problem?+
With 59 percent acceptance, it's a filter problem that separates candidates who see the pattern from those who don't. It's not a gimme, but it's not a final-round gauntlet either. Getting it right under time pressure proves you can recognize and code a standard pattern cleanly.
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