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Find maximum value of Sum(i*arr[i]) with only rotations on given array allowed


The task of maximizing the sum of the products of each element and its position when presented with an array of integers turns into an intriguing puzzle. This issue frequently arises in scenarios involving resource allocation, where it is crucial to maximise resource utilization.

Understanding the Problem

Given an array arr of n integers, the objective is to find the maximum value of ∑i=0n-1 (i×arr[i]) by rotating the array elements. A rotation involves shifting all elements one position to the right, with the last element moving to the first position.

Naive Approach: Brute Force

A straightforward but inefficient approach involves generating all possible rotations and computing the sum for each rotation. However, this approach has a time complexity of O(n2), making it impractical for larger arrays.

Optimized Approach: Mathematical Insight

An optimized strategy makes use of a mathematical realization. The difference between the original array's sum and the cyclic sum represents the change in sum after one rotation. This can be stated as follows:

Change in sum =sum-n×arr[n-1]

Before rotation, the sum of the indices is multiplied by the corresponding array elements in the formula.

Implementing the Algorithm

Iterating through the array to determine the initial sum and the sum change for each rotation is the optimized method. We can determine the maximum value of by monitoring the maximum sum and its rotation index ∑i=0n-1(i×arr[i]).

Handling Edge Cases

Think about edge situations where the array is null or has just one element. The maximum sum in these circumstances is zero.

Complexity Analysis

As we traverse the array twice-once to determine the initial sum and again to determine the maximum sum after rotations-the optimized approach has an O(n) time complexity. As we use the fewest possible variables to achieve intermediate results, the space complexity remains O(1).

Analyzing the Approach

To achieve our goal, we'll take the next course of action:

1. Calculating the Initial Sum

The initial sum will be calculated in the first step using the array elements in their original, unrotated state. We'll use this amount as our starting point to make comparisons as we rotate.

2. Determining the Rotations

The array will then undergo rotations as we iterate through it. We will calculate the sum of the products of the array elements and their corresponding indices for each rotation. We can find the rotations that produce higher values by analysing these sums.

3. Maximizing the Sum

After analysing how rotations affect the sum of products, we can determine which rotation produces the highest sum. The elements will be rotated in the most advantageous way to increase the sum's overall value.



Maximum sum of i * arr[i] after rotations: 40

The input array [1, 2, 3, 4, 5] in this example yields a maximum sum of 40 after rotations. The programme uses a mathematical insight-based approach to solve the issue effectively. To test various scenarios, you can swap out the arr with your own array.

The provided code defines a Python function called max_sum_with_rotations that calculates the maximum possible sum of the product of array elements and their respective indices after performing rotations on the array. In other words, it finds the arrangement of array elements that yields the highest sum when each element is multiplied by its index.

The purpose of the code is to demonstrate how to find the maximum possible sum of the product of array elements and their indices by rotating the array. Each rotation shifts the elements, and the goal is to find the arrangement that maximizes the sum of products.

Advantages of the Proposed Approach

The strategy described in this article has the following benefits:

1. Calculation Efficiency:

By utilising list comprehension, the implementation efficiently calculates the sum of products for each rotation. This allows rotation scenarios to be evaluated fairly quickly, even for arrays with a large number of elements.

2. Ideal Solution:

The method ensures the identification of the ideal rotation that maximises the sum of products through systematic rotation and evaluation. This guarantees that the algorithm always returns the highest possible value.

3. Simple Implementation:

The Python code made available for the implementation is clear-cut and simple to understand. It has a logical flow that corresponds to the article's earlier step-by-step methodology.

4. Versatile Application:

Although the underlying idea of optimisation through rotation can be applied to other situations, this particular problem only applies to rotated array elements. The abilities gained from comprehending this issue can be applied to a wider variety of problems.

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