Multiply left and right array sum

Summary

Given an array, we need to multiply the sum of elements at the left side with the sum of elements at the right side. The problem can be solved using a simple algorithm that iterates over the array and calculates the sums.

Detailed Explanation

To solve this problem, we iterate over the array from both ends (left and right) and keep track of the cumulative sum of elements on each side. Once we reach the middle element, we calculate the product of the left and right sums by multiplying the two cumulative sums.

Here is a step-by-step breakdown of the solution:

Initialize two variables left_sum and right_sum to 0.
Iterate over the array from both ends (left and right).
For each element, add its value to the corresponding cumulative sum (left_sum or right_sum).
When we reach the middle element, calculate the product of the left and right sums by multiplying left_sum and right_sum.
Return the product as the result.

Time complexity: O(n), where n is the length of the array. Space complexity: O(1), since we only use a constant amount of space to store the cumulative sums.

Optimized Solutions

Java

public int multiplyLeftAndRight(int[] arr) { int left_sum = 0; for (int i = 0; i < arr.length / 2; i++) { left_sum += arr[i]; } int right_sum = 0; for (int i = arr.length / 2; i < arr.length; i++) { right_sum += arr[i]; } return left_sum * right_sum; }