CodingMediumcod-g835

Subject Number theoryLevel Mid–Senior~20 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 n up to 10^12. Counting via per-element gcd is too slow; instead factorize n and apply the product formula phi(n) = n * product over distinct prime factors p of (1 - 1/p), implemented with integer arithmetic. Return 0 for n <= 0.

Implement

euler_totient(n: int) → int

Examples

in[12]out4

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.