Apollo.io coding interview
questions, leaked.
4 problems reported across recent Apollo.io interviews. Top patterns: array, hash table, stack. The list below is what most reported candidates actually saw, plus the honest play if you can't grind all of it.
Apollo.io's assessment leans hard on array manipulation and hash-table work, with a stack problem thrown in to catch you off guard. You're looking at four problems across medium and hard difficulty. Most candidates arrive prepped for arrays but choke when hash tables and stacks combine under time pressure. That's where StealthCoder acts as your invisible safety net during the live assessment. If you freeze on the sliding-window string problem or the stack-sequence validator, a working solution surfaces in seconds, invisible to the proctor. The good news: the patterns are learnable in a week if you know where to focus.
Top problems at Apollo.io
| # | Problem | Diff | Frequency | Pass % | Patterns |
|---|---|---|---|---|---|
| 01 | Minimum Window Substring | HARD | 100.0 | 45% | Hash Table · String · Sliding Window |
| 02 | Validate Stack Sequences | MEDIUM | 100.0 | 70% | Array · Stack · Simulation |
| 03 | Subarray Sum Equals K | MEDIUM | 93.2 | 45% | Array · Hash Table · Prefix Sum |
| 04 | Evaluate Reverse Polish Notation | MEDIUM | 93.2 | 55% | Array · Math · 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 Apollo.io OA. The proctor cannot see it. Screen share cannot detect it. Built by a senior engineer who knows the OA is theater. This is the script.
Get StealthCoder- array3 · 75%
- hash table2 · 50%
- stack2 · 50%
- string1 · 25%
- sliding window1 · 25%
- simulation1 · 25%
- prefix sum1 · 25%
- math1 · 25%
Three of the four problems center on arrays, making it the dominant topic by far. Hash tables appear in two problems, often paired with arrays to solve prefix-sum and subarray challenges. Stacks show up twice but in different contexts: once with simulation logic, once with math operations. The hard problem, Minimum Window Substring, combines hash tables, strings, and sliding windows into a single beast. Most candidates drill arrays independently and never practice hash-table + array combinations under time pressure. Start with Subarray Sum Equals K because it teaches you the hash-table-as-memory pattern that transfers to window problems. Then hit Validate Stack Sequences to get comfortable with the stack-simulation hybrid. Minimum Window Substring is your final stress test. When you're live and the subarray problem doesn't click immediately, StealthCoder is the hedge that keeps you moving forward.
Companies with similar patterns
If you prepped for Apollo.io, these companies recycle ~60% of the same topics.
You've seen the list.
Now make sure you pass Apollo.io.
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. Built by a senior engineer who knows the OA is theater. This is the script. Works on HackerRank, CodeSignal, CoderPad, and Karat.
Apollo.io interview FAQ
Should I spend more time on arrays or hash tables for Apollo.io?+
Arrays dominate with 3 of 4 problems, but hash tables appear in the two hardest array problems. Don't just practice arrays in isolation. Drill the hash-table + array combination (like Subarray Sum Equals K) first. It teaches the memory pattern you'll need.
Is stack knowledge required for Apollo.io's assessment?+
Yes, stack appears in two problems, including one that mixes stack with simulation logic. You can't skip it. Spend a day on basic stack operations, then practice Validate Stack Sequences and Evaluate Reverse Polish Notation back-to-back.
How much time should I spend on the hard problem?+
Minimum Window Substring combines three topics and sits at hard difficulty. Don't practice it first. Master the medium problems and the sliding-window pattern on strings separately, then combine them. Expect it to feel unmanageable until you've seen each piece individually.
What order should I drill these four problems?+
Start with Subarray Sum Equals K (array plus hash-table foundation), then Validate Stack Sequences (stack plus simulation), then Evaluate Reverse Polish Notation (reinforces stack logic), then Minimum Window Substring (the hardest, ties everything together).
Will one week be enough to prepare for Apollo.io?+
Yes, if you focus. Only four problems and no easy difficulty means the bar is medium-to-hard. Drill each problem's pattern, not just its solution. Practice under time pressure starting day four. StealthCoder covers whatever pattern you didn't have time to master.