A monotonic array is an array whose elements, from left to right, are entirely non-increasing, or entirely non-decreasing. Return true if the given array is monotonic.
Algorithm for monotonic array (1):
Check if the array is increasing or decreasing
If increasing, check if the array is monotonic increasing
If decreasing, check if the array is monotonic decreasing
If the array is monotonic increasing, return true
If the array is monotonic decreasing, return true
If the array is neither monotonic increasing nor monotonic decreasing, return false
Algorithm for monotonic array (1):
Check if the array is increasing or decreasing
If increasing, check if the array is monotonic increasing
If decreasing, check if the array is monotonic decreasing
If the array is monotonic increasing, return true
If the array is monotonic decreasing, return true
If the array is neither monotonic increasing nor monotonic decreasing, return false