Largest Substring Between Two Equal Characters
A easy-tier problem at 68% community acceptance, tagged with Hash Table, String. Reported in interviews at Zoho and 0 others.
You're 15 minutes into your Zoho assessment and you see this problem. Substring between two equal characters. Acceptance rate is 68%, which means one in three candidates either overcomplicates it or walks into a trap. The trick isn't complex, but it's easy to miss under pressure. You need the distance between the first and last occurrence of each character, find the max, and move on. If the pattern doesn't click in the moment, StealthCoder solves it invisibly during your screen share, so you don't waste time on an easy problem.
Companies that ask "Largest Substring Between Two Equal Characters"
Largest Substring Between Two Equal Characters 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 engineer who got tired of watching his cohort grind for six months and still get filtered at the OA stage.
Get StealthCoderThe pattern is straightforward once you see it. For each character in the string, track the first index where it appears and the last index where it appears. The length of the substring between them is last minus first minus one. Store all those lengths and return the max. Most candidates either try to build actual substrings in memory (wasteful), or they iterate multiple times when one pass with a hash table suffices. The trap is thinking you need to find contiguous regions. You don't. Just find characters that appear more than once, measure the span, and you're done. Common mistake: forgetting to subtract one from the distance, or thinking you need to validate that every character in between also appears. You don't. This problem is fast if you've internalized hash table patterns. If you blank on how to structure the lookup during the assessment, StealthCoder surfaces a working solution in seconds without the proctor seeing a thing.
Pattern tags
You know the problem.
Make sure you actually pass it.
Largest Substring Between Two Equal Characters 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. Built by an engineer who got tired of watching his cohort grind for six months and still get filtered at the OA stage. Works on HackerRank, CodeSignal, CoderPad, and Karat.
Largest Substring Between Two Equal Characters interview FAQ
Is this actually an easy problem or does the difficulty rating lie?+
The 68% acceptance rate confirms it's genuinely easy. The concept is trivial: find distance between first and last occurrence of each character. The mistake people make is overthinking it. A hash table tracks indices. One pass. Done. No hidden trick.
Will Zoho ask this exact problem or just this pattern?+
Zoho has reportedly asked this. Whether they repeat it or a variant depends on their interview cycle. Either way, the underlying logic of 'first occurrence, last occurrence, measure span' shows up in substring and span problems repeatedly across assessments.
What's the one mistake that kills most attempts?+
Forgetting that you need last_index minus first_index minus one, not plus one. Or building actual substring objects instead of just measuring distance. Both burn unnecessary time. A second mistake: re-scanning the string for each character instead of using one pass with a hash table.
How does this relate to the Hash Table topic?+
Hash tables are the core here. You store the first and last index of every character in O(1) average time. Without it, you'd iterate multiple times or use substring operations that bloat memory. The hash table makes the solution linear and clean.
If I haven't drilled this pattern, will I be able to solve it under pressure?+
It's 68% acceptance, so most people manage. But under time pressure, if the pattern doesn't click immediately, you could waste 10 minutes second-guessing yourself. That's where StealthCoder becomes the hedge: invisible solution in seconds if you hit a wall.
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