input: Write a function to determine if an array can be sorted in non-decreasing order by performing any number of unimodal rotations. An unimodal rotation is defined as shifting the front segment of the array to the back without changing the order of the elements. If it is possible, return True; otherwise, return False. If the array is empty, return True.
  assert move_one_ball([3, 4, 5, 1, 2])==True
  assert move_one_ball([3, 5, 10, 1, 2])==True
  assert move_one_ball([4, 3, 1, 2])==False
  assert move_one_ball([3, 5, 4, 1, 2])==False
  assert move_one_ball([])==True
output: def move_one_ball(arr):
      if not arr:
          return True
      n = len(arr)
      pivot = 0
      for i in range(1, n):
          if arr[i] < arr[i-1]:
              pivot = i
              break
      if pivot == 0:
          return True
      for i in range(pivot, n-1):
          if arr[i] > arr[i+1]:
              return False
      return arr[-1] <= arr[0]