README.md

1588. Sum of All Odd Length Subarrays

Given an array of positive integers arr, calculate the sum of all possible odd-length subarrays.

A subarray is a contiguous subsequence of the array.

Return the sum of all odd-length subarrays ofarr.

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

Solutions (Rust)

1. Solution

implSolution{pubfnsum_odd_length_subarrays(arr:Vec<i32>) -> i32{letmut d = (arr.len()asi32 + 1) / 2;letmut prev = d;letmut ret = 0;for i in0..(arr.len() / 2){let j = arr.len() - 1 - i; ret += (arr[i] + arr[j])* prev; d -= match arr.len() % 2{0 => 1, _ => 2*(1 - i asi32 % 2),}; prev += d;}if arr.len() % 2 == 1{ ret += arr[arr.len() / 2]* prev;} ret }}