Sum of All Odd Length Subarrays

In this lab, you are tasked with implementing a function that calculates the sum of all possible odd-length subarrays of a given array of positive integers. A subarray is defined as a contiguous subsequence of the given array.

The function signature is:

/**
 * @param {number[]} arr
 * @return {number}
 */
var sumOddLengthSubarrays = function(arr) {
    
};

Examples

1. Input: arr = [1,4,2,5,3]
   Output: 58
   Explanation: The odd-length subarrays of arr and their sums are:
   [1] = 1
   [4] = 4
   [2] = 2
   [5] = 5
   [3] = 3
   [1,4,2] = 7
   [4,2,5] = 11
   [2,5,3] = 10
   [1,4,2,5,3] = 15
   If we add all these together we get 1+4+2+5+3+7+11+10+15=58

2. Input: arr = [1,2]
   Output: 3
   Explanation: There are only 2 subarrays of odd length, [1] and [2]. Their sum is 3.

3. Input: arr = [10,11,12]
   Output: 66

Constraints

• 1 <= arr.length <= 100
• 1 <= arr[i] <= 1000

Follow up

Can you solve this problem in O(n) time complexity?