How to convert List<List<int>> to an array of arrays

Question

What is the best way to convert a list into an array of type int[][] ?

List<List<int>> lst = new List<List<int>>();

Answer 1

int[][] arrays = lst.Select(a => a.ToArray()).ToArray();

Answer 2

It's easy with LINQ:

lst.Select(l => l.ToArray()).ToArray()

If you really wanted two-dimentional array ( int[,] , not int[][] ), that would be more difficult and the best solution would probably be using nested for s.

Answer 3

you can easily do it using linq.

int[][] arrays = lst.Select(a => a.ToArray()).ToArray();

but if you want another way you can loop through the list and manually generate the 2d array.

how to loop through nested list

Answer 4

There's no library function to do this.

You'll need to do this with loops.

int[][] newlist = new int[lst.Size][];
for (int i = 0; i < lst.Size; i++)
{
    List<int> sublist = lst.ElementAt(i);
    newlist[i] = new int[sublis.Size];
    for (int j = 0; j < sublist.Size; j++)
    {
        newlist[i][j] = sublist.ElementAt(j);
    }
}

There you go!

Answer 5

If you don't have any restriction on using List<int[]> instead of List<List<int>> than use List<int[]> and then convert it into array of array using .ToArray() at end of list object.

Example for first converting List<List<int>> to List<int[]>

    List<int[]> listOfArray=new List<int[]>();
    List<List<int>> yourList=[someValue];
    foreach(var listItem in yourList){
        listOfArray.Add(listItem.ToArray());
    }

Example For List<int[]> to int[][] :

  int[][] jaggedArray= listOfArray.ToArray(); //voila you get jagged array or array of array