class Solution(object):
    def wiggleMaxLength(self, nums):
        """
        :type nums: List[int]
        :rtype: int
        """
        if not nums or len(nums) == 1:
            return len(nums)
        current_num, prev_num = nums[0], nums[0]
        count, trend = 0, None
        for current_num in nums:
            if not trend:
                if current_num > prev_num:
                    trend = "down_to_up"
                    count += 2
                elif current_num < prev_num:
                    trend = "up_to_down"
                    count += 2
            elif trend == "down_to_up":
                if current_num < prev_num:
                    count += 1
                    trend = "up_to_down"
            elif trend == "up_to_down":
                if current_num > prev_num:
                    prev_num = current_num
                    count += 1
                    trend = "down_to_up"
            prev_num = current_num
        if trend == None:
            count = 1
        return count