# Check if it is possible to sort the array after rotating it in Python

PythonServer Side ProgrammingProgramming

Suppose we have a list of numbers called nums, we have to check whether we can sort nums or not by using rotation. By rotation we can shift some contiguous elements from the end of nums and place it in the front of the array.

So, if the input is like nums = [4,5,6,1,2,3], then the output will be True as we can sort by rotating last three elements and send them back to first.

To solve this, we will follow these steps −

• n := size of nums
• if nums is sorted, then
• return True
• otherwise,
• status := True
• for i in range 0 to n - 2, do
• if nums[i] > nums[i + 1], then
• come out from loop
• i := i + 1
• for k in range i to n - 2, do
• if nums[k] > nums[k + 1], then
• status := False
• come out from loop
• if status is false, then
• return False
• otherwise,
• if nums[n - 1] <= nums, then
• return True
• return False

## Example

Let us see the following implementation to get better understanding −

Live Demo

def solve(nums):
n = len(nums)
if all(nums[i] <= nums[i + 1] for i in range(len(nums) - 1)):
return True
else :
status = True
for i in range(n - 1) :
if nums[i] > nums[i + 1] :
break
i += 1
for k in range(i, n - 1) :
if nums[k] > nums[k + 1]:
status = False
break
if not status:
return False
else :
if nums[n - 1] <= nums:
return True
return False
nums = [4,5,6,1,2,3]
print(solve(nums))

## Input

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

## Output

True