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Recursion for Coding Interviews in Python

Invert an Array

Explore how to invert an array recursively by flipping its elements so the first becomes last and vice versa. Understand key base cases and the step-by-step process behind each recursive call to successfully reverse the array using Python.

We'll cover the following...

What does “Invert an Array” mean?

Our task is to flip the elements of the array, meaning we will make the first element of the array the last element, the second element the second last element, and so on.

Inverting an array
Inverting an array

Implementation

Python 3.5
def reverse(array):
  # Base case1
  if len(array) == 0: # If we encounter an empty array, simply return an empty array
    return []
  
  # Base case2
  elif len(array) == 1 : # Inverting an array of size 1 returns the same array
   return array
  # Recursive case
  return [array[len(array) - 1]] + reverse(array[:len(array) - 1])
  # The first part is storing the last element to be appended later
  # The second part is calling another instance of the same function with the last element removed
# Driver Code
array = [1, 2, 3, 4]
print(reverse(array))

Explanation

In the code snippet above, we break the last element of the array, which will be added to the front of the array.

In each function call, we continue breaking the last element and ...