Is Maximum Alternating Subarray Sum With One Deletion easy or hard?

It is a medium-difficulty problem with an acceptance rate of about 30%. The brute force is easy to write, but finding the O(n) state transitions for the deletion case is the hard part. If you can derive the sign-inheritance rule for deletions, the rest of the code follows directly.

How to solve Maximum Alternating Subarray Sum With One Deletion in O(n)?

Scan the array once and maintain DP values for the best alternating sum ending at each index. Keep one set of states for subarrays with no deletion yet and another for subarrays where one element has been removed. When you delete an element, the next kept element takes the deleted element's sign, so that transition comes from two positions back. Track a global maximum across all states.

Maximum Alternating Subarray Sum With One Deletion Python/Java solution?

Python and Java solutions both use the same O(n) DP with rolling variables instead of a full DP table. In Python, you update the state variables in a loop over the array and return the global maximum. In Java, the logic is identical, with long used for sums to avoid overflow on large inputs.

What is the best approach for Maximum Alternating Subarray Sum With One Deletion?

The best approach is a single-pass dynamic programming solution that tracks sign states at each index, with separate states for whether a deletion has been used. It runs in O(n) time and uses O(1) extra space. Each index only depends on the previous two indices, so you never need to revisit earlier elements.

Is Maximum Alternating Subarray Sum With One Deletion asked at Google/Amazon/Meta?

FleetCode tags this problem under General, so it is not mapped to a specific company in our data. Check company-tagged question lists on other platforms for recent interview reports. The DP pattern it uses appears often in interviews, so practicing it is useful regardless of company.

What data structure is used in Maximum Alternating Subarray Sum With One Deletion?

No special data structure is required. The solution uses the input array plus a few scalar variables that store DP states for each sign and deletion status. Constant extra memory is enough because each state only needs the values from the previous one or two indices.

What is the time complexity of Maximum Alternating Subarray Sum With One Deletion?

The optimal solution runs in O(n) time, where n is the length of the array, because it makes one left-to-right pass with constant work per element. A brute force that tries every subarray and every deletion runs in O(n^3). The O(n) DP uses O(1) extra space.

4072. Maximum Alternating Subarray Sum With One Deletion - Practice Online

You are given an integer array nums.

You may delete at most one element from nums, then choose a subarray of the resulting array.

Return the maximum possible alternating sum of the chosen subarray.

The alternating sum of an array is the sum of its elements at even indices minus the sum of its elements at odd indices. The chosen subarray is reindexed starting from 0 before calculating its alternating sum.

Example 1:

Input: nums = [5,-5,1]

Output: 11

Explanation:

Choose not to delete an element and select the entire array. Its alternating sum is 5 - (-5) + 1 = 11, which is the maximum possible.

Example 2:

Input: nums = [10,-5,-100]

Output: 110

Explanation:

Delete nums[1] = -5 to obtain [10,-100], then select the entire resulting array. Its alternating sum is 10 - (-100) = 110, which is the maximum possible.

Example 3:

Input: nums = [4,7]

Output: 7

Explanation:

Choose not to delete an element and select the subarray [7]. Its alternating sum is 7, which is the maximum possible.

Constraints:

1 <= nums.length <= 10⁵
-10⁵ <= nums[i] <= 10⁵