[801] Minimum Swaps To Make Sequences Increasing

https://leetcode.com/problems/minimum-swaps-to-make-sequences-increasing/description/

• algorithms
• Medium (32.83%)
• Source Code: 801.minimum-swaps-to-make-sequences-increasing.py
• Total Accepted: 12.9K
• Total Submissions: 37.6K
• Testcase Example: '[1,3,5,4]\n[1,2,3,7]'

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].

# coding: utf-8
class Solution(object):
    def minSwap(self, A, B):
        """
        :type A: List[int]
        :type B: List[int]
        :rtype: int
        """
        swap, keep = [99999999] * len(A), [99999999] * len(A)
        swap[0], keep[0] = 1, 0
        for i in range(1, len(A)):

            if A[i]>A[i-1] and B[i]>B[i-1]:
                swap[i] = swap[i-1] + 1
                keep[i] = keep[i-1]

            if A[i]>B[i-1] and B[i]>A[i-1]:
                swap[i] = min(swap[i], keep[i-1]+1)
                keep[i] = min(keep[i], swap[i-1])

        return min(swap[-1], keep[-1])


# A, B = [1,2,4,8,10,12,14,15,16,18,20,24,26,27,32,33,35,36,39,40], [0,5,6,8,10,13,14,15,17,21,23,25,26,27,30,32,34,37,38,39]
# A, B = [1, 3, 5, 4], [1, 2, 3, 7]
# A, B = [1, 4, 3, 4, 7], [1, 2, 5, 6, 5]
#
#
# A, B = [0,3,5,8,9], [2,1,4,6,9]
# s = Solution()
# print s.minSwap(A, B)