Average between Indices

Given an array arr of size n, and two intervals x and y. Find the average of elements which lies between the given intervals inclusively.

Input Format

First Parameter - number n

Second Parameter - array arr of size n

Third Parameter - number x

Fourth Parameter - number y

Output Format

Return the decimal value

Example 1:

Input:
    6
    6 2 5 4 3 1
    2
    5
Output:
    3.25
Explanation:
    The elements between indices 2 and 5 are 5, 4, 3 and 1. The Average is: 
         (5 + 4 + 3 + 1) / 4 = 3.25

Example 2:

Input:
    2
    7 2
    0
    1
Output:
    4.5
Explanation:
    The elements between indices 0 and 1 are 7 and 2. The average is:
        (7 + 2) / 2 = 4.5

Constraints

• 0 <= n <= 10⁴
• -10⁴ <= arr[i] <= 10⁴
• 0 <= x <= y < n
• Expected Time Complexity: O(n)
• Expected Space Complexity: O(1)