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Let's call an array arr a mountain if the following properties hold: arr.length >= 3, there exists some index i (0 < i < arr.length - 1) such that arr[0] < arr[1] < ... < arr[i - 1] < arr[i] > arr[i + 1] > ... > arr[arr.length - 1]. Given a mountain array arr, return the index i such that arr[0] < arr[1] < ... < arr[i - 1] < arr[i] > arr[i + 1] > ... > arr[arr.length - 1].
An integer array arr representing a mountain array.
Return an integer index i denoting the peak index of the mountain array.
3 <= arr.length <= 10^4. 0 <= arr[i] <= 10^6. arr is a mountain array.
Example 1
Input
[0,1,0]
Output
1
Explanation
The peak element is at index 1 with value 1.
Example 2
Input
[0,2,1,0]
Output
1
Explanation
The peak element is at index 1 with value 2.