wiggle subsequence

class (object):
    def wiggleMaxLength(self, nums):
        """
        :type nums: List[int]
        :rtype: int
        """
        if len(nums) <= 1:
            return len(nums)
        dp = [1 for _ in range(len(nums))] 
        dp_direction = [None for _ in range(len(nums))] # dp_direction[i] longest wiggle sequence ending with nums[i] with direction pos True or neg False
        for i in range(1, len(nums)):
            for j in range(i):
                if dp_direction[j] is None:
                    if nums[i] > nums[j]:
                        dp_direction[i] = True
                        dp[i] = dp[j] + 1
                    if nums[i] < nums[j]:
                        dp_direction[i] = False
                        dp[i] = dp[j] + 1
                elif nums[i] > nums[j] and not dp_direction[j]:
                    if dp[i] < dp[j] + 1:
                        dp[i] = dp[j] + 1
                        dp_direction[i] = True
                elif nums[i] < nums[j] and dp_direction[j]:
                    if dp[i] < dp[j] + 1:
                        dp[i] = dp[j] + 1
                        dp_direction[i] = False
        return max(dp)