How should I practice Maximum Sum with at Most Three Two-Element Tiles?

Start by reading the full statement, solve the visible examples, then compare the pattern against related Marshall Wace phone screen problems in FastPrep.

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FastPrep tags this as a Marshall Wace phone screen coding practice problem when the problem catalog has that company and stage context.

Maximum Sum with at Most Three Two-Element Tiles

Marshall Wace● MediumNEW GRADPHONE SCREEN

Problem statement

You are given an integer array A and at most three tiles. Each tile covers exactly two neighbouring array elements.

Tiles cannot overlap.
A tile cannot extend outside the array, even partially.
You may use fewer than three tiles, including zero.

Return the greatest possible sum of the covered elements.

Function

solution(A: int[]) → int

Examples

Example 1

A = [1,2,3,4]return = 10

Use two tiles to cover [1,2] and [3,4]. Their combined sum is 10.

Example 2

A = [-5,-2,-1]return = 0

Using no tiles is better than covering a negative-sum pair.

Example 3

A = [5,1,1,5,1,1,5]return = 18

Cover index pairs (0,1), (2,3) and (5,6). Each pair sums to 6, giving 18.

Example 4

A = [7]return = 0

No complete two-element tile fits.

Constraints

0 <= A.length <= 200000.
-10^8 <= A[i] <= 10^8.