Implementing the Merge Sort Algorithm with Python

Merge sort is based on the divide and conquer algorithm, with three core steps: divide (split the array into left and right subarrays until single elements), recursively sort (recursively sort each subarray), and merge (merge the ordered subarrays into a single ordered array). Taking the array [3, 1, 4, 2] as an example, after decomposition, each subarray is recursively sorted and then merged into [1, 2, 3, 4]. The Python implementation includes a merge function (to merge two ordered subarrays in sequence) and a recursive sorting function (to decompose and recursively call merge). Its characteristics: time complexity O(n log n), space complexity O(n) (requires additional storage for merge results), and it is a stable sort (the relative order of equal elements remains unchanged).