How to "alternate" two data tables

Question

Take these two lists:

List 1

Red green blue

List 2

Brown Red Blue Purple Orange

I am looking for a way to combine these lists together to create:

List 3

Brown Red Green Blue Purple Orange

I think the basic rules are as follows:

1) Insert at the top the list of any line falling before the first common line (for example, Brown comes before the first common line, Red);

2) Insert items between the lines if both lists have two items (for example, in list 1, a green color is inserted between red and blue); and

3) Insert the lines at the bottom if there is no “gap” between them (for example, in list 2, the orange is inserted at the bottom).

Lists are stored in a DataTable. I assume that I will have to switch between them during the iteration, but it is difficult for me to define a method for combining strings.

Thanks for any help.

- Brent

Answer 1

I think something in this direction should do this for you:

Dictionary<string, float> clrs = new Dictionary<string, float>(); float i = 0; foreach (string s in largeList) clrs.Add(s, i++); float lastIndex = 0; for (int j = 0; j < smallList.Count; j++) { if (largeList.Contains(smallList[j])) lastIndex = clrs[smallList[j]]; else clrs.Add(smallList[j], lastIndex + 0.5f); } var sorted = from c in clrs.Keys orderby clrs[c] select c; return sorted.ToList<string>(); 

it does not accept duplicates in any list and that function is passed to the larger list as a large list.

Answer 2

If you want to join two standard lists and don't care about sorting, you can use something like this:

 var list1 = new[] { "Red", "Green", "Blue" }; var list2 = new[] { "Brown", "Red", "Blue", "Purple", "Orange" }; var result = new List<string>( list2 ); result.AddRange( list1.Except( list2 ) ); 

Trying to keep some special order will be difficult. For example, suppose list2 does not contain red, what should be the first element: brown or red? Suppose list1 is yellow, but list2 is yellow second. What should be the order?

If you are trying to combine two data tables, there is a Merge method in the DataTable, which allows you to combine one DataTable into another.

DataTable.Merge