用python写个最简短的归并排序代码

下面是一个简单的 Python 归并排序实现：

def merge_sort(arr):
    if len(arr) > 1:
        mid = len(arr) // 2
        left_half = arr[:mid]
        right_half = arr[mid:]
        merge_sort(left_half)
        merge_sort(right_half)
        i = j = k = 0
        while i < len(left_half) and j < len(right_half):
            if left_half[i] < right_half[j]:
                arr[k] = left_half[i]
                i += 1
            else:
                arr[k] = right_half[j]
                j += 1
            k += 1
        while i < len(left_half):
            arr[k] = left_half[i]
            i += 1
            k += 1
        while j < len(right_half):
            arr[k] = right_half[j]
            j += 1
            k += 1
    return arr

调用 `merge_sort` 函数即可对一个列表进行归并排序：

arr = [3, 8, 1, 7, 4, 2]
sorted_arr = merge_sort(arr)
print(sorted_arr)  # [1, 2, 3, 4, 7, 8]