A difficulty tag is a promise about time and about what a good answer contains. It is measured for a candidate who has prepared, not for a beginner.
Level | Time for a prepared candidate | What is expected | Typical shape |
|---|---|---|---|
Easy | 3 minutes | The right answer. | One rule in play. Expected if you know the language or the tool flow. |
Medium | 6 to 8 minutes | The answer and the why: you name the rule that decides it. | Two rules interact (for example signedness and shift, solve order and distribution, sampling and reset). |
Hard | 10 to 15 minutes | The answer, the why, the trap and a fix. | A subtle ordering, scheduling or solver interaction that experienced engineers also miss. |
Section | Easy | Medium | Hard |
|---|---|---|---|
9 | 15 | 0 | |
8 | 13 | 3 | |
6 | 17 | 1 | |
8 | 11 | 5 | |
4 | 13 | 7 | |
4 | 20 | 0 | |
5 | 17 | 2 | |
4 | 15 | 5 | |
8 | 10 | 6 | |
8 | 10 | 6 | |
8 | 10 | 6 |
Score every attempt before you read the solution. Be strict. The score tells you what to do next.
Score | Meaning | What to do |
|---|---|---|
0 | No idea. You could not start. | Read the hint and solution, then re-attempt cold tomorrow. |
1 | Right idea, wrong result. You found the topic but made an error in the trace. | Find the line where the trace went wrong. Re-attempt in two days. |
2 | Right result, no reason. You may have guessed or recalled it. | Treat it as a miss. Write the rule in one sentence, then re-attempt in two days. |
3 | Right result and the reason. You named the rule. | Good. Add the trap: what does a wrong answer look like? |
4 | Right result, reason, the trap and a fix. You also named what changes if the snippet is mutated. | Done. Revisit once, a week later, as a check. |
If you used the hint, take one point off. A hard puzzle needs a 4 to count as done. For an easy puzzle a 3 is enough. Track your score per section: the lowest section average is where tomorrow's hour goes.
Interviewers rarely switch puzzles; they mutate one. Change blocking to nonblocking, add disable iff, flip |-> to |=>, add solve...before, or move the sample point. Each puzzle's follow-up shows the escalation to expect, so an easy puzzle in your first minutes can turn into a hard one in the next five.
Easy then medium: the same snippet, one more rule added.
Medium then hard: the interviewer asks what changes if the order, the clock or the tool changes.
Hard then discussion: the interviewer asks how you would prove it, check it or fix it in a real testbench.