我可以使用什么算法在C＃中对此分支列表进行排序？

Question

I'm trying to create an ordered branching list of categories, so I can find any subcategories and add "-" at the start; and also any subcategories that category might have and add "--" etc.

My test class properties looks like this:

    public int Id { get; set; }
    public int OrderInList { get; set; }
    public int ParentId { get; set; }
    public IList<TestCategories> Subcategories { get; set; }

Example:

Books
-Special Offers
--Fiction
-eBooks 
--Pdf
--Mobi
Maps
-United Kingdom
--Cumbria
--West Yorkshire

I have a default root level category with Id: 1 , ParentId: 1 and OrderInList: 1 .
So the order of the above would look something like:

Id   | ParentId  |  OrderInList   
 2         1             1      //Books
 3         2             1      //-Special Offers
 4         3             1      //--Fiction
 5         2             2      //-eBooks
 6         5             1      //--Pdf
 7         5             2      //--Mobi
 8         1             2      //Maps
 9         8             1      //-United Kingdom
 10        9             1      //--Cumbria
 11        9             2      //--West Yorkshire

How can I sort a completely unordered list to look something like the above?

Answer 1

This kind of sorting is called Topological Sorting . The easiest way to sort a list topologically is using a depth-first recursive search: the order in which you leave the nodes is reverse topological. If you need to know the depth of a node in a tree so that you know how many dashes to place in front of a name, you can add an int level variable to your depth-first recursive method.

You can borrow an implementation from Rosetta Code - it does not have one in C#, but the one in Java should be easy enough to translate.