I dont understand the problem, the explanation is laking for details in my oppinion.

Broken in JS but here is my solution

function processData(input) {
    const arrStartIndex = input.lastIndexOf('\n');
    const finalArr = input.substring(arrStartIndex + 1).split(' ');
    const sortedArr = finalArr.sort((a, b) => a - b);
    const middleNumber = (sortedArr.length / 2)
    const secondHalf = sortedArr.slice(middleNumber)
    const firstHalf = sortedArr.slice(0, middleNumber)
    const result= [...firstHalf, ...secondHalf.reverse()].join(' ')
    return result;
}

My results are the same as expected, but it says it is incorrect

it is broken in js :(

   const [_, length, rawArr] = input.split('\n');

const arr = rawArr.split(' ').sort((a, b) => a - b);


let mid = Math.floor(length / 2);

[arr[mid], arr[length - 1]] = [arr[length - 1], arr[mid]]

let left = mid + 1;
let right = length - 2;
while (left < right) {
    [arr[left], arr[right]] = [arr[right], arr[left]];
    left++;
    right--;
}

const str = arr.join(' ');
const strTrim = str.trim();


console.log(strTrim);

This challange is broken for multiple languages and, well, that's just sad