The Cycle Detector

A medium Python interview practice problem on DataDriven. Write and execute real python code with instant grading.

Domain

Python

Difficulty

medium

Seniority

L3

Problem

Given a list where each index i has next_pointers[i] = next index (or -1 for tail), return True if starting from any index leads to a cycle. Actually: follow starting from index 0 and detect whether any index is revisited before hitting -1 or out-of-range.

Summary

Follow the chain long enough and you might end up where you started.

Practice This Problem

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