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**yuhaowang001**

You are given an array of positive and negative integers. If a number n at an index is positive, then move forward n steps. Conversely, if it's negative (-n), move backward n steps. Assume the first element of the array is forward next to the last element, and the last element is backward next to the first element. Determine if there is a loop in this array. A loop starts and ends at a particular index with more than 1 element along the loop. The loop must be "forward" or "backward'.

**Example 1:**
Given the array [2, -1, 1, 2, 2], there is a loop, from index 0 -> 2 -> 3 -> 0.

**Example 2:**
Given the array [-1, 2], there is no loop.

**Note:**
The given array is guaranteed to contain no element "0".

Can you do it in **O(n)** time complexity and **O(1)** space complexity?

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