Generate combinations of multiple arrays dynamically

Question

Hi I want to generate combinations from multiple array elements. A1={abc} & A2={def} & A3={123} My result should be abcdef123adaeafbdbebfcdcecfa1a2a3b1b2b3c1c2c3d1d2d3e1e2e3f1f2f1ad1ad2ad3ae1ae2ae3af1af2af3bd1bd2bd3... I am able to generate this when the source list is given.But i want to achieve the same when the source is N and the elements in each array is N. Please help to generate combinations.

Vulpes · Answer

Not the easiest of combination questions but the following should work not only for N = 3 but for any other value of N: using System; using System.Collections.Generic; using System.Text; using System.Linq; class Program { static void Main(string[] args) { int N = 3; var A = new string[N][]; A[0] = new string[]{a b c}; A[1] = new string[]{d e f}; A[2] = new string[]{1 2 3}; /* We first need to get all possible combinations of the N arrays. To do this we consider all integers from 1 to 2 ^ N - 1 expressed in binary. The positions of the 1's in these binary strings will tell us whether to include a particular array in a given combination or not. We order these by the number of 1's in each binary string and then reverse the strings so that the results will be presented in the required order. */ int max = (int)Math.Pow(2 N) - 1; string[] B = Enumerable.Range(1 max). Select(i => Convert.ToString(i 2).PadLeft(N '0')). OrderBy(s => s.ToCharArray().Count(c => c == '1')). Select(s => new string(s.Reverse().ToArray())). ToArray(); /* Now get all the combinations by choosing one element from each array specfied in each binary string using recursion. */ List C = GetCombinations(A B); Console.WriteLine(String.Join( C)); Console.ReadKey(); } static List GetCombinations(string[][] A string[] B) { var C = new List (); var sb = new StringBuilder(); for(int x = 0; x { GetNextLevel(A B x 0 sb C); } return C; } static void GetNextLevel(string[][] A string[] B int x int y StringBuilder sb List C) { if (y { if (B[x][y] == '1') { foreach(string t in A[y]) { sb.Append(t); GetNextLevel(A B x y + 1 sb C); sb.Length = sb.Length - 1; } } else { GetNextLevel(A B x y + 1 sb C); } } else { C.Add(sb.ToString()); } } } The output is: abcdef123adaeafbdbebfcdcecfa1a2a3b1b2b3c1c2c3d1d2d3 e1e2e3f1f2f3ad1ad2ad3ae1ae2ae3af1af2af3bd1bd2bd3be1be2be3 bf1bf2bf3cd1cd2cd3ce1ce2ce3cf1cf2cf3

vimala v · Answer

Thanks for your code Vulpes.. Working like a charm..