leetcode852

int peakIndexInMountainArray(vector<int>& A) {
    int Len = A.size();
    int position = -;
    for (int i = ; i < Len - ; i++)
    {
        if (A[i] > A[i - ] && A[i] > A[i + ])
        {
            position = i;
            break;
        }
    }
    return position;
}