Sum of All Odd Length Subarrays
Given an array of positive integers arr, return the sum of all possible odd-length subarrays of arr.
Given an array of positive integers arr, return the sum of all possible odd-length subarrays of arr.
A subarray is a contiguous subsequence of the array.
Follow up:
Could you solve this problem in O(n) time complexity?
Example 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
Example 2
Input: arr = [1,2]
Output: 3
Explanation: There are only 2 subarrays of odd length, [1] and [2]. Their sum is 3.
Example 3
Input: arr = [10,11,12]
Output: 66
Constraints
- 1 <= arr.length <= 100
- 1 <= arr[i] <= 1000
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