Sum of All Subarrays | 3 Approaches Explained | Java | AlgoXploration

[@AlgoXploration]

public int sumOfSubarrays(int[] arr) {
// Initialize a variable 'sum' to store the total sum of all subarray sums.
int sum = 0;
// Get the length of the input array 'arr'.
int n = arr.length;
// Loop through each element of the array.
for (int i = 0; i < n; i++) {
// Calculate how many subarrays include the element at index 'i'.
// The element at index 'i' appears in (i + 1) subarrays starting from index 0 to i,
// and it also appears in (n - i) subarrays ending at index i to (n - 1).
// Therefore, the total number of subarrays that include arr[i] is (i + 1) * (n - i).
int c = (i + 1) * (n - i);
// Multiply the element arr[i] by the count 'c' and add it to the total sum.
// This ensures that arr[i] contributes to the sum of all subarrays where it appears.
sum += (arr[i] * c);
}
// Return the total sum of all subarrays.
return sum;
}