题目 

 

分析 

代码 

class Solution {
public:
    int wiggleMaxLength(vector<int>& nums) {
        if(nums.size() < 2) return nums.size();
        int ret = 0,left = 0,right = 0;

        for(int i = 0;i < nums.size()-1;i++){
            right = nums[i+1] - nums[i];
            if(right == 0) continue;
            if(left * right <= 0) ret++;
            left = right;
        }
        return ret+1;
    }
};