redbus coding interview
questions, leaked.
2 problems reported across recent redbus interviews. Top patterns: dynamic programming, stack, array. The list below is what most reported candidates actually saw, plus the honest play if you can't grind all of it.
RedBus is running a compact assessment with just two problems, but don't mistake brevity for ease. You're looking at a hard problem and a medium, both touching dynamic programming and stack patterns that demand precision. The hard problem is Trapping Rain Water, a multi-pattern beast that tests whether you can think in 2D space and optimize without brute force. If you've never seen it, it stings. If you have, it's a confidence builder. StealthCoder is your safety net if you blank on the optimal approach mid-assessment and need a working solution in seconds.
Top problems at redbus
| # | Problem | Diff | Frequency | Pass % | Patterns |
|---|---|---|---|---|---|
| 01 | Trapping Rain Water | HARD | 100.0 | 65% | Array · Two Pointers · Dynamic Programming |
| 02 | Minimum Deletions to Make String Balanced | MEDIUM | 90.1 | 66% | String · Dynamic Programming · Stack |
Frequencies derived from public community-tagged interview reports. Click a row to view on LeetCode.
You have a week, maybe less. You can't out-grind the list above. StealthCoder runs invisibly during the actual redbus OA. The proctor cannot see it. Screen share cannot detect it. Made for the engineer who has done the work but might still blank with a webcam pointed at him.
Get StealthCoder- dynamic programming2 · 100%
- stack2 · 100%
- array1 · 50%
- two pointers1 · 50%
- monotonic stack1 · 50%
- string1 · 50%
Dynamic programming and stack show up in both problems, meaning RedBus wants to see if you can recognize when to build state versus when to iterate with a monotonic structure. Trapping Rain Water is the spike: it's a classic that appears in every serious platform, and it rewards precomputation and clever pointer logic. The medium string problem is more straightforward but still requires you to track balance and deletions, which again leans DP. Array and two-pointers are supporting patterns. If you've drilled these two problems before, you're walking in calm. If not, stack-based problems are easy to panic on under time pressure. That's where StealthCoder hedges you: even if the optimal monotonic approach doesn't click during the live OA, you get a working solution without losing the round.
Companies with similar patterns
If you prepped for redbus, these companies recycle ~60% of the same topics.
You've seen the list.
Now make sure you pass redbus.
Memorizing every problem above in a week is a fantasy. StealthCoder is the hedge: an AI overlay that's invisible during screen share. It reads the problem on screen 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.
redbus interview FAQ
Should I study dynamic programming or stack first for RedBus?+
Both appear equally in their problem set, but Trapping Rain Water (the hard) is the filter. Master the stack-and-DP hybrid approach to that problem first. It teaches you when to precompute and when to iterate. Then move to string DP on the medium problem.
Is two-pointer technique critical for this assessment?+
It appears in only one problem but is core to the optimal solution for Trapping Rain Water. You don't need to grind separate two-pointer problems, but you must understand how it pairs with monotonic stack logic in that specific problem.
How much time should I spend on Trapping Rain Water before the assessment?+
It's 50 percent of your assessment. Spend 2 to 3 hours understanding the three main approaches: brute force, DP, and monotonic stack. Only the last two are acceptable at interview speed. Know which one you'll code under pressure.
Is the medium string problem easier than the hard?+
Yes, but only if you recognize it's a DP state-tracking problem. Stack comes in as a supporting pattern. It's a good warm-up problem, but don't underestimate the state-management part of the solution.
What if I can't optimize Trapping Rain Water during the assessment?+
Brute force buys you partial credit and time to move on. But a working suboptimal solution beats nothing. Have a fallback coded before you sit down so you don't waste the hard problem slot.