SRE Python drills

The index of the Python notes doubles as a drill set: small HackerRank-style SRE questions on a sample Nginx combined access log, each answered with the smallest correct algorithm and its stated time and space cost.

The drills

Drill	Technique	Cost
Count 5xx requests	Stream the file line by line and read the status after the quoted request	O(n) time, O(1) space
Count each status	dict.get(status, 0), then sorted by count	O(n) scan, O(k log k) sort
Top N paths	Split the quoted request into method, path, protocol; slice [:n]	O(m) scan, O(k log k) sort
Duplicate request IDs	A seen set and a duplicates set	O(n) average
Two Sum	A dictionary of complements	O(n) time and space
Maximum fixed-window count	Slide the window, adding the entering value and removing the leaving one	O(n) time, O(1) space

As listed in the source.¹

Answering in an interview

flowchart LR
    accTitle: Interview answer sequence
    accDescr: Confirm the contract, explain with a small example, write the smallest runnable solution, test edge cases, then state complexity.
    A[Confirm inputs and outputs] --> B[Explain with an example]
    B --> C[Smallest runnable solution]
    C --> D[Test edge cases]
    D --> E[State time and space]

Confirm input, output, and invalid-input behavior; explain the algorithm on a small example; write the smallest runnable solution; test empty input, duplicates, no result, and boundaries; then state time and space complexity.¹

Related

• Text processing: the same log parsing with awk and uniq.
• Python language fundamentals
• Python program structure
• Domain index

Footnotes

1. Python SRE HackerRank Quick Reference, original ↩ ↩²