Generate combinations of set inside set without intersection with values of current set in C# -

what (easy read , fast runtime) way of generating combinations of set (set of items) inside other set (set of groups) without intersection values of current set (items in same group)?

for example have 2 simple classes. group contains set of item

public class group {     public string name { get; set; }     public iset<item> items { get; set; } }  public class item {     public string name { get; set; } } 

as result have set of groups each 1 contains set of items configured like:

var groupa = new group {     name = "a",     items = new hashset<item> {          new item { name = "a1" },          new item { name = "a2" },          new item { name = "a3" }      } }; var groupb = new group {     name = "b",     items = new hashset<item> {          new item { name = "b1" },          new item { name = "b2" },      } }; var groupc = new group {     name = "c",     items = new hashset<item> {          new item { name = "c1" },          new item { name = "c2" },          new item { name = "c3" },          new item { name = "c4" },      } }; var groupsset = new hashset<group>(); groupsset.add(groupa); groupsset.add(groupb); groupsset.add(groupc); 

what way groupsset combinations (1) , (2):

1)

a1, b1, c1 a1, b1, c2 a1, b1, c3 a1, b1, c4 a1, b2, c1 a1, b2, c2 a1, b2, c3 a1, b2, c4 a2, b1, c1 a2, b1, c2 a2, b1, c3 a2, b1, c4 a2, b2, c1 a2, b2, c2 a2, b2, c3 a2, b2, c4 a3, b1, c1 a3, b1, c2 a3, b1, c3 a3, b1, c4 a3, b2, c1 a3, b2, c2 a3, b2, c3 a3, b2, c4 

2)

a1 a2 a3 b1 b2 c1 c2 c3 c4 a1, b1 a1, b2 a2, b1 a2, b2 a3, b1 a3, b2 a1, c1 a1, c2 a1, c3 a1, c4 a2, c1 a2, c2 a2, c3 a2, c4 a3, c1 a3, c2 a3, c3 a3, c4 b1, c1 b1, c2 b1, c3 b1, c4 b2, c1 b2, c2 b2, c3 b2, c4 a1, b1, c1 a1, b1, c2 a1, b1, c3 a1, b1, c4 a1, b2, c1 a1, b2, c2 a1, b2, c3 a1, b2, c4 a2, b1, c1 a2, b1, c2 a2, b1, c3 a2, b1, c4 a2, b2, c1 a2, b2, c2 a2, b2, c3 a2, b2, c4 a3, b1, c1 a3, b1, c2 a3, b1, c3 a3, b1, c4 a3, b2, c1 a3, b2, c2 a3, b2, c3 a3, b2, c4 

when items same roup not intersected each other, items other groups?

amount of groups , amount of items in group may differ.

order of items inside combination not relevant.

thank you.

you're looking cartesian product, can generated using linq's selectmany, or in query syntax:

var query = in groupa.items             b in groupb.items             c in groupc.items             select new group()             {                 items = new hashset<item>() { a, b, c },             };    var groupsset = new hashset<group>(query); 

if don't know number of groups @ compile time can use this solution eric lippert cartesian product of unknown number of sequences:

public static ienumerable<ienumerable<t>> cartesianproduct<t>(this ienumerable<ienumerable<t>> sequences) {     ienumerable<ienumerable<t>> emptyproduct = new[] { enumerable.empty<t>() };     return sequences.aggregate(         emptyproduct,         (accumulator, sequence) =>         accseq in accumulator         item in sequence         select accseq.concat(new[] { item })); } 

which allows write:

var groups = new[] { groupa.items, groupb.items, groupc.items };  var query2 = groups.cartesianproduct()     .select(combination => new group     {         items = new hashset<item>(combination),     });