Canonical coding interview
questions, leaked.
3 problems reported across recent Canonical interviews. Top patterns: array, math, stack. The list below is what most reported candidates actually saw, plus the honest play if you can't grind all of it.
Canonical's interview is lean. Three problems across two easy and one medium. The topics aren't exotic: arrays, strings, math, stack basics. You're not fighting a monster problem bank here. The catch is efficiency. Each problem tests whether you can write clean, working code under pressure. If you blank on stack notation or two-pointer merging during the assessment, StealthCoder runs invisibly and surfaces a working solution. That's your real hedge.
Top problems at Canonical
| # | Problem | Diff | Frequency | Pass % | Patterns |
|---|---|---|---|---|---|
| 01 | Divide a String Into Groups of Size k | EASY | 100.0 | 67% | String · Simulation |
| 02 | Evaluate Reverse Polish Notation | MEDIUM | 79.6 | 55% | Array · Math · Stack |
| 03 | Merge Sorted Array | EASY | 65.6 | 53% | Array · Two Pointers · Sorting |
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 Canonical OA. The proctor cannot see it. Screen share cannot detect it. Built by an engineer who got tired of watching his cohort grind for six months and still get filtered at the OA stage.
Get StealthCoder- array2 · 67%
- math1 · 33%
- stack1 · 33%
- string1 · 33%
- simulation1 · 33%
- two pointers1 · 33%
- sorting1 · 33%
Arrays dominate the dataset, appearing twice across the core problems. String manipulation and simulation show up once each, paired with the easier tier. The medium problem, Evaluate Reverse Polish Notation, is the only one that touches math and stack depth. This tells you Canonical values solid fundamentals over algorithmic wizardry. Spend your prep time on two-pointer merging and array iteration patterns. Stack problems are lower frequency here, so if you haven't internalized postfix notation, don't panic. StealthCoder is the safety net when you hit the medium problem live and need a working stack solution in real time without tanking your score.
Companies with similar patterns
If you prepped for Canonical, these companies recycle ~60% of the same topics.
You've seen the list.
Now make sure you pass Canonical.
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 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.
Canonical interview FAQ
How many array problems should I solve before the Canonical OA?+
At least five to ten solid ones. Arrays show up twice in their top problems, and both require different skills: one uses two pointers and sorting, the other uses basic string indexing. Pick classics on merging and partitioning, then shift to stack if you need a confidence boost.
Is the medium problem harder than the two easy ones?+
Yes. Evaluate Reverse Polish Notation requires stack knowledge and careful operator precedence. If you've never implemented postfix evaluation, treat it as your weak spot now, not during the live OA. An hour on this problem pays off.
Should I study stack before or after arrays?+
Arrays first. Two of three top problems are array-heavy, and they're both easier tier. Get those locked down in a day. Then spend an evening on stack operations using the RPN problem as your drill.
What if I run out of time and can't finish all three?+
The two easy problems are more likely to appear. Nail Merge Sorted Array and Divide a String Into Groups of Size k first. If you have time left, tackle RPN. Even getting two done cleanly beats half-working medium code.
Is simulation a topic I need to study separately?+
No. Simulation appears once, paired with string splitting in the easy problem. It's not a deep topic here. Focus on string iteration and array slicing. The simulation is just the problem's wrapper, not a separate skill set.