if you draw a line to connect all points in nums, this question is asking how many turning point in the line.

start with the second element (i = 1), find the left and right number which is different from current element. If current element is a dip or peak, then it is a turning point.

the first element is a turning point

the last element is a turning point too if it is different from the second last element.

```
class Solution {
public:
int wiggleMaxLength(vector<int>& nums)
{
int size = nums.size();
if(size<2) return size;
int ans = 1, left, right;
for(int i = 1; i < size; i++ )
{
if(nums[i]==nums[i-1]) continue;
left = right = i;
while(left>0 && nums[--left]==nums[i]){};
while(right<size-1 && nums[++right]==nums[i]){};
if((nums[i]>nums[left] && nums[i]>nums[right])||
(nums[i]<nums[left] && nums[i]<nums[right])) ans++;
}
if(nums[size-2]!=nums[size-1]) ans++;
return ans;
}
};
```