CodingMediumcod-g412

Subject Number theoryLevel Mid–Senior~25 minCommon in Algorithms & data structures interviewsIndustries Software development

Question

Compute Euler's totient phi(n): the count of integers in [1, n] that are coprime to n. For example phi(9) = 6 (1,2,4,5,7,8). Constraints: 1 <= n <= 1e12, with phi(1) = 1 by convention. Use the product formula over distinct prime factors; do not loop over all integers up to n.

Implement

euler_totient(n: int) → int

Examples

in[9]out6

What a strong answer looks like

State your approach and its time/space complexity out loud before you optimize. Handle the edge cases (empty input, duplicates, overflow), and say why you chose this over the brute force. Green tests are the floor, not the grade.

Learn the concepts

Vibe coding: describe the solution in plain language (or narrate it) and the coach grades your approach. Generating runnable code from your description is coming next.

Run or narrate your approach, then ask the coach.