本题要考虑三种情况：

1. 上下坡中有平坡
2. 数组首尾两端
3. 单调坡中有平坡

class Solution {
    public int wiggleMaxLength(int[] nums) {
        if(nums.length <= 1) return nums.length;
        int curdiff = 0;
        int prediff = 0;
        int result = 1;
        for(int i = 1; i< nums.length;i++){
            curdiff = nums[i] - nums[i - 1];
            if((curdiff > 0 && prediff <= 0) || (curdiff < 0 && prediff >= 0)){
                result++;
                prediff = curdiff;
            }
        }
        return result;
    }
}