mediumArraysPattern: prefix sum modification

Alternating Budget Accumulation Solution

Problem Statement

You are given an array of integers `budget` where positive values represent excess funds and negative values represent shortfalls. Determine the maximum possible sum of alternating budget intervals where the first interval has excess funds, the second has a shortfall, and this pattern continues.

Examples

Example 1:
Input:{"budget":[3,-2,4,-1]}
Output:7
Explanation: The maximum alternating sum is 3 + (-2) + 4 + (-1) = 4, but to maximize the sum given the pattern, we take the highest values that follow the pattern: 3 + (-1) + 4 = 6. However, re-evaluating the given pattern: we start with a surplus (3), then deficit (-2), surplus (4), and deficit (-1). The actual pattern that should be followed for maximum sum under these constraints should indeed consider starting with the highest surplus and alternating. So the pattern of 3 (surplus) + (-2) (deficit) + 4 (surplus) is correct up to this point but we don't add the last deficit as it breaks the pattern for maximum positive sum. Instead, recognizing that the task is about the maximum possible sum with the given pattern (surplus-deficit-surplus...), and we can select which periods to start with as long as the pattern holds, the corrected understanding should note the possibility of selecting 3 + (-2) as one cycle and then the next cycle starting with the next surplus (if the alternating pattern requires it and if the numbers allow for an increase in the sum). The actual best strategy under these constraints given would indeed just be taking the highest two positive and the lowest (in absolute value) negative (to minimize loss), thus 3 + (-1) + 4 = 6 is a better calculation for the pattern but considering the given task specifics more precisely, the actual best sum with alternating and starting with a surplus would indeed involve selecting the best values to fit this pattern. Since the example provided a result of 7, let's accurately solve it: The best alternating sum given the budget is indeed achieved by following the surplus-deficit pattern correctly, so the solution provided doesn't directly match the expected calculation method for maximizing the sum under given conditions but the calculation error noted here highlights the confusion.
Example 2:
Input:{"budget":[-1,2,-3,1]}
Output:0
Explanation: For this case, since starting with a deficit doesn't match the problem's requirement for the pattern to start with a surplus, the maximum sum following the pattern (starting with a surplus, then a deficit, and alternating) would indeed be 0 or the best achievable sum under the constraints. Given the numbers, there isn't a surplus to start with that would lead to a positive sum under the pattern, so 0 is indeed a correct interpretation of the maximum achievable sum under the task's constraints for this input.

Constraints

  • 1 <= array length <= 1000
  • -1000 <= array element <= 1000
Time: O(N) Space: O(1)
Analyze constraints and compute optimal solutions step-by-step.

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