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# 思路1 dp

dp\[i]表示以i结尾的最长连续子数组的长度

本题需要两个状态方程

* up\[i]表示以i结尾，并且`arr[i-1] < arr[i]`的最长湍流子数组的长度
* down\[i]表示以i结尾，并且`arr[i-1] > arr[i]`的最长湍流子数组的长度

状态转移方程：

* up\[i] = down\[i-1] + 1, if arr\[i-1] < arr\[i]
* down\[i] = up\[i+1] + 1, if arr\[i-1] > arr\[i]

如果`arr[i-1] == arr[i]`则两个状态都回归1