【动态规划】376. 摆动序列

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