Quick Select Generic Solution for string & number

QuickSelect.js

function partition(arr, lo, hi, compare) {
    // Choose a random pivot and move it to the start
    const randomIndex = Math.floor(Math.random() * (hi - lo + 1)) + lo;
    swap(arr, lo, randomIndex);
    const pivot = arr[lo];

    let i = lo + 1; // Start just after the pivot
    let j = hi;

    while (i <= j) {
        // Find the first element greater than or equal to the pivot
        while (i <= hi && compare(arr[i], pivot) < 0) i++;

        // Find the first element less than or equal to the pivot
        while (j >= lo && compare(arr[j], pivot) > 0) j--;

        if (i >= j) break;

        swap(arr, i, j);
        i++;
        j--;
    }

    // Place the pivot in its correct position
    swap(arr, lo, j);
    return j; // Return the index of the pivot
}

const swap = (arr, i, j) => [arr[i], arr[j]] = [arr[j], arr[i]];

function quickSelect(arr, k, compare) {
    let lo = 0;
    let hi = arr.length - 1;

    while (lo <= hi) {
        const j = partition(arr, lo, hi, compare);
        if (j === k) {
            return arr[k];
        } else if (j < k) {
            lo = j + 1;
        } else {
            hi = j - 1;
        }
    }
    return null; // In case k is out of bounds
}

const compare = (a, b) => BigInt(a) - BigInt(b);

function findKthLargest(arr, k) {
    return quickSelect(arr, arr.length - k, compare);
}

function kthSmallestNumber(arr, k) {
    return quickSelect(arr, k - 1, compare);
}