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Released: April 19, 2026 at 12:13 AM

Max Subarray One Deletion

Find the maximum sum of a non-empty subarray, potentially after deleting at most one element from it. This means you can either take a regular subarray sum or take a subarray sum after removing one element within it.

Problem Statement

Given an array of integers `arr`, return the maximum possible sum of a non-empty subarray. You are allowed to delete at most one element from the chosen subarray. The subarray must remain non-empty after deletion (if any). For example, if you select the subarray `[5]` and delete `5`, the resulting subarray is empty, which is an invalid operation. However, if you choose `[5, -1, 3]` and delete `-1`, the sum is `5 + 3 = 8`. If you choose not to delete any element from `[5, -1, 3]`, the sum is `5 + (-1) + 3 = 7`. Your solution should determine the absolute maximum sum possible under these conditions. The constraints on `arr` are `1 <= arr.length <= 10^5` and `-10^4 <= arr[i] <= 10^4`.

Example Test Cases

Input:
arr = [1, -2, 0, 3]
Output:
4
Explanation:

Deleting -2 from the subarray [1, -2, 0, 3] yields [1, 0, 3] with sum 4. This is the maximum possible sum.

Input:
arr = [1, 2, 3]
Output:
6
Explanation:

No deletion is needed. The subarray [1, 2, 3] has sum 6, which is the maximum.

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