wiggle-subsequence

// 参考了：https://discuss.leetcode.com/topic/51893/two-solutions-one-is-dp-the-other-is-greedy-8-lines
// 另有：https://discuss.leetcode.com/topic/51946/very-simple-java-solution-with-detail-explanation

class Solution {
public:
    int wiggleMaxLength(vector<int>& nums) {
        int up = 1, down = 1;
        if (nums.size() <= 1) {
            return nums.size();
        }
        for (int i=1; i<nums.size(); ++i) {
            if (nums[i] < nums[i-1]) {
                down = up + 1;
            }
            else if (nums[i] > nums[i-1]) {
                up = down + 1;
            }
        }
        return max(up, down);
    }
};