find the kth smallest number in a list in csharp

main.cs
public static int QuickSelect(int[] arr, int k)
{
    int left = 0, right = arr.Length - 1;

    while (true)
    {
        if (left == right)
            return arr[left];

        int pivotIndex = Partition(arr, left, right);
        if (k == pivotIndex)
            return arr[k];
        else if (k < pivotIndex)
            right = pivotIndex - 1;
        else
            left = pivotIndex + 1;
    }
}

private static int Partition(int[] arr, int left, int right)
{
    int pivotIndex = new Random().Next(left, right);
    int pivotValue = arr[pivotIndex];

    Swap(arr, pivotIndex, right);
    int storeIndex = left;

    for (int i = left; i < right; i++)
    {
        if (arr[i] < pivotValue)
        {
            Swap(arr, i, storeIndex);
            storeIndex++;
        }
    }

    Swap(arr, storeIndex, right);
    return storeIndex;
}

private static void Swap(int[] arr, int i, int j)
{
    int temp = arr[i];
    arr[i] = arr[j];
    arr[j] = temp;
}
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main.cs
int[] arr = { 5, 2, 4, 1, 3 };
int k = 2;
int kthSmallest = QuickSelect(arr, k - 1);  // subtract 1 because we're zero-indexed

Console.WriteLine(kthSmallest);  // output: 2
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