Question

I have an array with different numbers (integers). The length of that array is not set, so it is different every time I run my program. Then I have two other arrays and I want the program to evaluate all possibilites for the distribution of the first array into the other two arrays. For example:

Array 1: 1,3,5

Now the programm should make the other two arrays for example like this:

Array 2: 1,3
Array 3: 5

Or like this:

Array 2: 1,5
Array 3: 3

Answer 1

Consider the placement of an item as a binary digit, then you see that all binary number with the same number of digits as the number of items represent all possible combinations.

So, for three items you have 8 possible combinations:

000: [1,3,5], []
001: [3,5], [1]
010: [1,5], [3]
011: [5], [1,3]
100: [1,3], [1]
101: [3], [1,5]
110: [1], [3,5]
111: [], [1,3,5]

You can calculate the number of possible combinations using 1 << theArray.Length.

You can get a specific combination (0 to possible-1) using:

public static void GetArrays(int[] arr, int combination, out int[] arr1, out int[] arr2) {
  List<int> a = new List<int>();
  List<int> b = new List<int>();
  foreach (int value in arr) {
    if ((combination & 1) == 1) {
      b.add(value);
    } else {
      a.add(value);
    }
    combination >>= 1;
  }
  arr1 = a.ToArray();
  arr2 = b.ToArray();
}