maximum difference in array

求array中最大差值 要求：1. i<j 2.a[i]<a[j] 3. a[i] is odd ,a[j] is even

class Solution(object):
    def maxSubArray(self, nums):
        """
        :type nums: List[int]
        :rtype: int
        """

        minimum = None
        res = None

        for num in nums:
            if num % 2 == 0:
                if minimum == None:
                    continue
                else:
                    if num > minimum:
                        res = max(res, num - minimum)
            else:
                if minimum == None:
                    minimum = num
                else:
                    minimum = min(num, minimum)

        return res