CodingMediumcod-g637

Subject Combinatorial countingLevel Mid–Senior~25 minCommon in Algorithms & data structures interviewsIndustries Software development

Question

n people stand in a circle numbered 1..n. Starting from person 1 and counting, every k-th person is eliminated; counting resumes from the next person. Return the 1-indexed position of the last survivor (the Josephus problem). Use the O(n) recurrence, not a simulation. Constraints: 1 <= n <= 100000, 1 <= k <= 10^9.

Implement

josephus_survivor(n: int, k: int) → int

Examples

in[7,3]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.