Minimum Adjacent Swaps to Reach the Kth Smallest Number — LeetCode 1850 Python Solution

class Solution:
    def getMinSwaps(self, num: str, k: int) -> int:
        def next_permutation(nums: List[str]) -> bool:
            n = len(nums)
            i = n - 2
            while i >= 0 and nums[i] >= nums[i + 1]:
                i -= 1
            if i < 0:
                return False
            j = n - 1
            while j >= 0 and nums[j] <= nums[i]:
                j -= 1
            nums[i], nums[j] = nums[j], nums[i]
            nums[i + 1 : n] = nums[i + 1 : n][::-1]
            return True

        s = list(num)
        for _ in range(k):
            next_permutation(s)
        d = [[] for _ in range(10)]
        idx = [0] * 10
        n = len(s)
        for i, c in enumerate(num):
            j = ord(c) - ord("0")
            d[j].append(i)
        arr = [0] * n
        for i, c in enumerate(s):
            j = ord(c) - ord("0")
            arr[i] = d[j][idx[j]]
            idx[j] += 1
        return sum(arr[j] > arr[i] for i in range(n) for j in range(i))