FallDown.cs

using System;

class FallDown
{
    static void Main()
    {
        int n = 8;

        uint[] numbers = new uint[n];

        for (int i = 0; i < n; i++)
        {
            string number = Console.ReadLine();
            numbers[i] = UInt32.Parse(number);
        }

        int[] onesInCol = new int[n];

        // get the 1's count in each column
        for (int col = 0; col < n; col++)
        {
            uint mask = 1U << col;

            for (int i = 0; i < n; i++)
            {
                if ((numbers[i] & mask) != 0)
                {
                    onesInCol[col]++;
                }
            }
        }

        uint[] newNumbers = new uint[n];

        // set the 1's in the respective columns of the numbers - bottom-up
        for (int col = 0; col < n; col++)
        {
            int i = n - 1;
            uint mask = 1U << col;
            while (onesInCol[col] > 0)
            {
                newNumbers[i] |= mask;
                onesInCol[col]--;
                i--;
            }
        }

        for (int i = 0; i < n; i++)
        {
            Console.WriteLine(newNumbers[i]);
        }
    }
}