Sorting an Array of Arrays in Python with Merge Sort: A Comprehensive Guide

Learn how to effectively sort an array of arrays in Python using merge sort, focusing on sorting based on specific criteria while maintaining order among similar elements.
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Sorting an Array of Arrays in Python with Merge Sort: A Comprehensive Guide

Sorting data effectively is a crucial skill in programming. Today, we'll explore how to sort an array of arrays in Python using the merge sort algorithm. Specifically, we'll tackle the challenge of sorting based on specific criteria: the last element within each array, while ensuring that similar items remain grouped together.

The Problem

You have an initial array of arrays that looks something like this:

[[See Video to Reveal this Text or Code Snippet]]

You want to sort this array based on the last element (the number) in each internal array, from the highest value to the lowest. Additionally, items with the same initial element (e.g., all ['a', 'new'] arrays) should remain next to each other.

The expected output should look like this:

[[See Video to Reveal this Text or Code Snippet]]

The Solution

To solve this issue using the merge sort algorithm, we'll make some key adjustments to our original code. Let's break it down into clear sections.

Merge Function

First, we adjust the merge function to accept a key argument. This function will dictate how we compare the elements of the arrays when merging:

[[See Video to Reveal this Text or Code Snippet]]

Merge Sort Function

Next, we modify the mergesort function to also take the key argument. This function recursively divides the array until it can be merged back together in sorted order:

[[See Video to Reveal this Text or Code Snippet]]

Putting It All Together

Now, we can define the sample array and invoke the mergesort function with a custom sorting key. Our key will ensure that we first sort by the last element (in descending order) and then by the first element (in ascending order):

[[See Video to Reveal this Text or Code Snippet]]

Expected Output

When you run this code, you should see the sorted output you desired:

[[See Video to Reveal this Text or Code Snippet]]

Conclusion

With these adjustments, you can effectively sort an array of arrays in Python based on specific criteria using the merge sort algorithm. By incorporating a key function, you clarify the sorting logic and maintain order among similar items. Happy coding!