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# Program to check right rotation forms increasing or decreasing array with first n natural numbers or not in Python

Suppose we have a list of numbers called nums, where n elements are present. We have to chesk whether we can make a list with first n natural numbers either in increasing or decreasing fashion, like [1, 2, ..., n] or [n, n - 1, ..., 1] by shifting nums to the right any number of times or not.

So, if the input is like nums = [5,6,1,2,3,4], then the output will be True, because we can shift them four times to make the array [1,2,3,4,5,6]

To solve this, we will follow these steps −

- n := size of nums
- for i in range 1 to n - 1, do
- if |nums[i - 1] - nums[i]| is not 1 and |nums[i - 1] - nums[i]| is not n-1, then
- return False

- if |nums[i - 1] - nums[i]| is not 1 and |nums[i - 1] - nums[i]| is not n-1, then
- return True

## Example

Let us see the following implementation to get better understanding −

def solve(nums): n = len(nums) for i in range(1, n): if abs(nums[i - 1] - nums[i]) != 1 and abs(nums[i - 1] - nums[i]) != n - 1: return False return True nums = [5,6,1,2,3,4] print(solve(nums))

## Input

[5,6,1,2,3,4]

## Output

True

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