We have two integer sequences A and B of the same non-zero length.
We are allowed to swap elements A[i] and B[i].  Note that both elements are in the same index position in their respective sequences.
At the end of some number of swaps, A and B are both strictly increasing.  (A sequence is strictly increasing if and only if A[0] < A[1] < A[2] < ... < A[A.length - 1].)
Given A and B, return the minimum number of swaps to make both sequences strictly increasing.  It is guaranteed that the given input always makes it possible.
Example:
Input: A = [1,3,5,4], B = [1,2,3,7]
Output: 1
Explanation: 
Swap A[3] and B[3].  Then the sequences are:
A = [1, 3, 5, 7] and B = [1, 2, 3, 4]
which are both strictly increasing.
Note:
A, B are arrays with the same length, and that length will be in the range [1, 1000].
A[i], B[i] are integer values in the range [0, 2000].
class Solution:
    def minSwap(self, A: List[int], B: List[int]) -> int:
        N = len(A)
        not_swap, swap = 0, 1
        for i in range(1, N):
            not_swap2 = swap2 = N 
            if A[i - 1] < A[i] and B[i - 1] < B[i]:
                swap2 = swap + 1
                not_swap2 = not_swap
            if A[i - 1] < B[i] and B[i - 1] < A[i]:
                swap2 = min(swap2, not_swap + 1)
                not_swap2 = min(not_swap2, swap)
            swap, not_swap = swap2, not_swap2
        return min(swap, not_swap)
class Solution:
    def minSwap(self, A: List[int], B: List[int]) -> int:
        N = len(A)
        not_swap, swap = 0, 1
        for i in range(1, N):
            not_swap2 = swap2 = N 
            if A[i - 1] < A[i] and B[i - 1] < B[i]:
                swap2 = swap + 1
                not_swap2 = not_swap
            if A[i - 1] < B[i] and B[i - 1] < A[i]:
                swap2 = min(swap2, not_swap + 1)
                not_swap2 = min(not_swap2, swap)
            swap, not_swap = swap2, not_swap2
        return min(swap, not_swap)