using System;

​

var input = new int[] { 3, 4, 1, 5, 2, 7, 4, 2, 6 };

​

var numberOfSubsets = (int)Math.Pow(2, input.Length);

​

var subsets = new int[numberOfSubsets][];

​

int nextEmptyIndex = 0;

​

// Add the empty set

subsets[nextEmptyIndex++] = new int[0];

​

foreach (int element in input)

{

    // Record the index of the end of the current elements.

    int stopIndex = nextEmptyIndex - 1;

​

​

    // Add the subsets of the previously existing elements

    // and the new element. Skip the empty set at index 0.

    for (int i = 0; i <= stopIndex; i++)

    {

        int newSubsetLength = subsets[i].Length + 1;

        int newSubsetIndex = nextEmptyIndex++;

        subsets[newSubsetIndex] = new int[newSubsetLength];

​

        Array.Copy(subsets[i], subsets[newSubsetIndex], subsets[i].Length);

        subsets[newSubsetIndex][newSubsetLength - 1] = element;

    }

}

​

for (int i = 0; i < subsets.Length; i++)

{

    Console.WriteLine($"subsets[{ i }] = { string.Join(", ", subsets[i]) }");

}

​