changing_sequence.py

#Have the function ChangingSequence(arr) take the array of numbers stored in arr and return the index 
#at which the numbers stop increasing and begin decreasing or stop decreasing and begin increasing. 
#For example: if arr is [1, 2, 4, 6, 4, 3, 1] then your program should return 3 because 6 is the last point in the array where the numbers were increasing and the next number begins a decreasing sequence.
# The array will contain at least 3 numbers and it may contains only a single sequence, increasing or decreasing. If there is only a single sequence in the array, then your program should return -1. Indexing should begin with 0.

def ChangingSequence(arr):
  for i in range(1, len(arr)-1):
    if (arr[i] > arr[i-1] and arr[i] > arr[i+1]) or (arr[i] < arr[i-1] and arr[i] < arr[i+1]):
      return i

  # code goes here
  return -1

# keep this function call here 
print(ChangingSequence(input()))
#我很为自己骄傲，这道题是我冷静思考，找到规律，总结规律，勇于尝试做出来的