Best Nonempty Subarray After At Most One Erasure

### Problem Choose a contiguous subarray of arr and optionally erase one of its elements. At least one chosen element must remain. Return the greatest sum attainable; deletion is optional. ```cpp class Solution { public: int maximumSum(vector<int>& arr); }; ``` ### Examples **Example 1:** ```text Input: arr = [4,-5,3,2] Output: 9 Explanation: Choose the full array and erase-5, retaining4+3+2. ``` **Example 2:** ```text Input: arr = [-4,-2,-7] Output: -2 Explanation: Keep the singleton-2. An empty result is forbidden. ``` ### Constraints - There are 1 to 100000 elements. - Each value is an integer in `[-10000,10000]`. ### Contract considerations The original interval is contiguous; after the optional deletion, its remaining elements need not be adjacent in the original array. ```hint Read the boundary condition If all entries are negative, may the chosen interval become empty after the optional erasure? ``` ### Boundary reminders The original interval is contiguous; after the optional deletion, its remaining elements need not be adjacent in the original array.