Get the maximum number in an array that is increasing then decreasing.

get_max.py

def get_max(arr, start, end):
    # arr of size 1
    if start == end:
        return arr[start]
    #arr of size 2, first element is larger than the second
    if start == end + 1 and arr[start] >= arr[end]:
        return arr[start]
    #arr of size 2, second element is larger than the first
    if end == start + 1 and arr[start] < arr[end]:
        return arr[end]

    #find the middle of the array
    #compare the middle element to its adjacent elements
    mid = (start + end)//2

    #if arr[mid] is larger than it's adjacent elements (mid-1, mid-2_
    # arr[mid] is the greatest element
    if arr[mid] >= arr[mid + 1] and arr[mid] >= arr[mid - 1]:
        return arr[mid]
    #if arr[mid] greater than the right element and less than the left element
    # we focus on the left side of the array and do the same logic of get_max()
    if arr[mid] > arr[mid + 1] and arr[mid] < arr[mid - 1]:
        return get_max(arr, start, mid-1)
    # otherwise, we focus on the right array and do the same logic of get_max()
    else:
        return get_max(arr, mid + 1, end)



test_cases =[
    [1, 3, 8, 15, 17, 9, 7, 2],
    [1, 3, 8, 15, 17],
    [3,2,5,6,7],
    [10,9,8,7,6,5,4,3,2,1],
    [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,6,5,4,3,2,1],
    [1,2,3,4,5,6,7,8,9,10,10,9,8,7],
    [1,1,1,1,1,1,1,1,1,1],
    [-1,6,4]
]
for test_case in test_cases:
    print(get_max(test_case,0,len(test_case)-1))