Pancake Sorting Python Solution with Tests

lcpy gen -n 969   # by problem number
lcpy gen -s pancake_sorting   # by problem name

Input: arr = [3,2,4,1]
Output: [4,2,4,3]
Explanation:
We perform 4 pancake flips, with k values 4, 2, 4, and 3.
Starting state: arr = [3, 2, 4, 1]
After 1st flip (k = 4): arr = [1, 4, 2, 3]
After 2nd flip (k = 2): arr = [4, 1, 2, 3]
After 3rd flip (k = 4): arr = [3, 2, 1, 4]
After 4th flip (k = 3): arr = [1, 2, 3, 4], which is sorted.

Input: arr = [1,2,3]
Output: []
Explanation: The input is already sorted, so there is no need to flip anything.
Note that other answers, such as [3, 3], would also be accepted.

class Solution:
    # Time: O(n^2)
    # Space: O(n) for the working copy
    def pancake_sort(self, arr: list[int]) -> list[int]:
        result: list[int] = []
        work = list(arr)
        for target in range(len(work), 1, -1):
            idx = work.index(target)
            if idx == target - 1:
                continue
            if idx != 0:
                result.append(idx + 1)
                work[: idx + 1] = work[idx::-1]
            result.append(target)
            work[:target] = work[target - 1 :: -1]
        return result