sales[i] is a shop's net result on day i. The owner wants to highlight two stretches of consecutive days that do not overlap (they may be adjacent), each non-empty, with the largest combined total. Return that maximum total.
Examples
Input: sales = [1, -2, 3, -1, 4, -5, 2]
Output: 8
Explanation: Days 2-4 total 6 and day 6 totals 2.
Input: sales = [-3, -1, -2]
Output: -3
Explanation: Both stretches must be non-empty; -1 and -2 is the best pair.
Constraints
2 <= len(sales) <= 10**5,-10**4 <= sales[i] <= 10**4.- Target complexity: O(n) time, O(n) space.
Goals
- Precompute the best subarray within every prefix and every suffix
- Combine them across a split point to enforce non-overlap