Minimum Swaps To Make Sequences Increasing

lcpy gen -n 801   # by problem number
lcpy gen -s minimum_swaps_to_make_sequences_increasing   # by problem name

Input: nums1 = [1,3,5,4], nums2 = [1,2,3,7]
Output: 1
Explanation:
Swap nums1[3] and nums2[3]. Then the sequences are:
nums1 = [1, 3, 5, 7] and nums2 = [1, 2, 3, 4]
which are both strictly increasing.

Input: nums1 = [0,3,5,8,9], nums2 = [2,1,4,6,9]
Output: 1

class Solution:
    # Time: O(n)
    # Space: O(1)
    def min_swap(self, nums1: list[int], nums2: list[int]) -> int:
        keep = 0
        swap = 1
        for i in range(1, len(nums1)):
            keep_next = swap_next = len(nums1)
            if nums1[i] > nums1[i - 1] and nums2[i] > nums2[i - 1]:
                keep_next = keep
                swap_next = swap + 1
            if nums1[i] > nums2[i - 1] and nums2[i] > nums1[i - 1]:
                keep_next = min(keep_next, swap)
                swap_next = min(swap_next, keep + 1)
            keep, swap = keep_next, swap_next
        return min(keep, swap)