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Grokking the Coding Interview Patterns

Circular Array Loop

Explore the fast and slow pointers approach to detect cycles in a circular array of integers. This lesson helps you understand how to check for repeated sequences with consistent direction, an essential technique for coding interviews involving cycle detection.

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Statement

There is a circular list of non-zero integers called nums. Each number in the list tells you how many steps to move forward or backward from your current position:

  • If nums[i] is positive, move nums[i] steps forward.

  • If nums[i] is negative, move nums[i] steps backward.

As the list is circular:

  • Moving forward from the last element takes you back to the first element.

  • Moving backward from the first element takes you to the last element.

A cycle in this list means:

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