Here is the interview question prompt, presented for reference.

We have an array of length 2 * n (even length) that consists of random integers.

[1, 3, 2, 6, 5, 4]

We are asked to create pairs out of these integers, like such:

[[1, 3], [2, 6], [5, 4]]

How can we divide up the pairs such that the sum of smaller integers in each pair is maximized?

Here's an example input: [3, 4, 2, 5]. The return value is 6 because the maximum sum of pairs is 6 = min(2, 3) + min(4, 5).

Note that negative numbers may also be included.

Constraints

• Length of the array <= 100000
• The values will always contain integer values between -1000 and 1000
• The final answer will always fit in the integer value
• Expected time complexity : O(nlogn)
• Expected space complexity : O(1)

You can see the full challenge with visuals at this link.