A Common-Sense Guide to Data Structures and Algorithms in Python, Volume 1

Unnecessary Recursive Calls

Here’s a recursive function that finds the greatest number from an array:

def max(array):
    if not array:
        return None

    if len(array) == 1:
        return array[0]

    if array[0] > max(array[1:]):
        return array[0]
    else:
        return max(array[1:])

The essence of each recursive call is the comparison of a single number (array[0]) to the maximum number from the remainder of the array. (To calculate the maximum number from the remainder of the array, we call the very max function we’re in, which is what makes the function recursive.)

We achieve the comparison with a conditional statement. The first half of the conditional statement is as follows:

if array[0] > max(array[1:]):
    return array[0] ...