Circular Array Loop
You are playing a game involving a circular array of non-zero integers nums. Each nums[i] denotes the number of indices forward or backward you must move if you are located at index i:
- If
nums[i]is positive, movenums[i]steps forward. - If
nums[i]is negative, moveabs(nums[i])steps backward.
Since the array is circular, moving forward from the last element puts you on the first element, and moving backward from the first element puts you on the last element.
A cycle in the array consists of a sequence of indices seq of length k where:
- Following the movement rules above results in the repeating index sequence
seq[0] -> seq[1] -> ... -> seq[k - 1] -> seq[0] -> .... - Every
nums[seq[j]]is either all positive or all negative. k > 1.
Return true if there is a cycle in nums, or false otherwise.
Follow up: Could you solve it in O(n) time complexity and O(1) extra space complexity?
Example 1
Input
nums = [2,-1,1,2,2]Output
trueIndices 0 -> 2 -> 3 -> 0 form a cycle of length greater than 1, and all nodes move in the same forward direction.
Example 2
Input
nums = [-1,-2,-3,-4,-5,6]Output
falseThe only cycle is of size 1, so it is not a valid cycle.
Constraints
- 1 <= nums.length <= 5000
- -1000 <= nums[i] <= 1000
- nums[i] != 0
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