Wiggle Subsequence

Problem: Wiggle Subsequence

When we are scanning the array, if we are going down, we should try to reach lowest possible consecutive number. For example, if the sequence looks like [3,2,1,2,0], we should going down to 1 so that we can go up at 2. If we go down to 3 and stop going down, we cannot reach longer subsequence. Also when we are going up, we should also try to reach largest possible consecutive number.

Code in Python:

class Solution(object):
    def wiggleMaxLength(self, nums):
        """
        :type nums: List[int]
        :rtype: int
        """
        if not nums: return 0

        direction, res = 0, 1
        for i in xrange(1, len(nums)):
            if direction == 0:
                if nums[i] != nums[i-1]: res += 1

                if nums[i] > nums[i-1]: direction = 1
                elif nums[i] < nums[i-1]: direction = -1
            elif nums[i] < nums[i-1] and direction == 1:
                res += 1
                direction = -1
            elif nums[i] > nums[i-1] and direction == -1:
                res += 1
                direction = 1
        return res