How should I practice Cyclic Shift to a Reverse-Sorted Array?

Start by reading the full statement, solve the visible examples, then compare the pattern against related TikTok online assessment problems in FastPrep.

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Cyclic Shift to a Reverse-Sorted Array

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Problem statement

You are given an integer array nums of length n.

For an integer t with 0 <= t < n, a cyclic t-shift moves the last t elements of nums to the beginning while preserving their order.

Return the value of t that transforms nums into the reverse-sorted array [n, n - 1, ..., 1]. If no such shift exists, return -1.

Function

solution(nums: int[]) → int

Examples

Example 1

nums = [3,2,1,5,4]return = 2

Moving the last two elements to the front produces [5,4,3,2,1], so t = 2.

Example 2

nums = [5,4,3,2,1]return = 0

The array already equals [5,4,3,2,1], so no shift is needed.

Example 3

nums = [1,2,3]return = -1

No cyclic shift produces [3,2,1], so the result is -1.

Constraints

For this exercise, assume 1 <= nums.length <= 100000.
For this exercise, assume -10^9 <= nums[i] <= 10^9.