C# programming:

Raul Roa

5y1.3k

Hi, How to get from a int list with the numbers 39 39 39 40 40, two list: ListA.Add(39 39 39); ListB.Add(40 40);Thanks.

11 Replies

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Rajanikant Hawaldar5y ago
Accepted answer
Hello Raul, check below
List<int> ListA = new List<int>() { 39, 39, 39, 40, 40 };
var groups = ListA.GroupBy(x => x, x => x).Select(y => y.ToList());
List<int> ListB = groups.ToList()[0];
List<int> ListC = groups.ToList()[1];
Rajanikant Hawaldar5y ago
@Raul, if ListA has more groups then use loop
Raul Roa5y ago
Hello, Thanks everyone for helping me. Finally I got what I needed.
Raul Roa5y ago
Hello Rajanikant Hawaldar, your solution is pretty good, but if my list has the values ListA = 39, 39, 39, 40, 40, 20, 20, 20, 20, your solution it is going to display the first two groups and then I have to add another code line: List ListD = groups.ToList[2]; What about if the ListA has 2000 groups. How to display any size of the ListA in a dataGridView control using your solution? I think I will need just one list (ListB) to record each group inside a double for() loop, so when the first group is recorded, use ListB.Clear(); and then record the second group and so on, this way I don't have to be worry how many groups there are in the ListA. Could you help me. Thanks
Anu Viswan5y ago
To be honest, the question is a bit unclear. Here is my assumption of what you are attempting to achieve and proposed solution.

You have a list of items such as "39 39 39 40 40". You would need to parse sub groups of the list, (39,39,39) and (40,40) in another list (lList B) and do some processing/work on them.

In this scenario, you could use IEnumerable.GroupBy. For example,
private IEnumerableint>> ParseGroups(List<int> completeList)
{
    return completeList.GroupBy(x=>x).Select(x=> x.ToList());
}
You could now use the method as
foreach(var collectionB in ParseGroups(listA))
{
// Do your work with collectionB
}
Hope that helps.
Raul Roa5y ago
Hello, thanks for helping me, your answer is correct, but my question it wasn't clear. I posted the list data ListA = 39, 39, 39, 40, 40 so this way people can understand what I really needed and that was a mistake. I just know that my list contains groups of equals numbers, but I don't know: 1) How many groups of equals numbers the list contain. 2) Which numbers contains the list. For example, the list could be ListA = 20, 20, 30, 30, 51, 51, 51, 51 but I don't know. What I want is go through the all ListA and compare its numbers for equality and record the first group in ListB (20, 20) and then clear the ListB, next record (30, 30) and clear it and finally record (51, 51, 51, 51). The following code it doesn't works: for (int i = 0; i < ListA.Count; i++) { for (int j =i+1; j < ListA.Count;j++) { if (ListA[j] == ListA[i] { // Update ListB with // ListB.Clear; ListB.Add(ListA[i]); } } } Thanks in advance.
Salman Beg5y ago
Hey use this below code,
int[] intArray = { 39, 39, 39, 40, 40 };
            List<int> listA = new List<int>();
            listA.AddRange(intArray);
            List<int> listB = new List<int>();
            List<int> listC = new List<int>();
            foreach (var e in listA)
            {
                if (e == 39)
                {
                    listB.Add(e);
                }
                else
                {
                    listC.Add(e);
                }
            }
Thanks
Raul Roa5y ago
Hello, I really don't understand the code in the link you send me. List ListB = new List(); List ListC = new List(); foreach (var e in ListA) { if () // What is the condition? }
Salman Beg5y ago
You can do that by using foreach loop. Goto the end of this below link and you can find two examples and you can apply any one. https://stackoverflow.com/questions/54129757/c-sharp-how-to-split-a-list-in-two-using-linq
Raul Roa5y ago
Hello Salman, but what I need is the opposite, I have the ListA 39 39 39 40 40 and what I want is split the ListA into two list ListB 39 39 39 and ListC 40 40, thanks
Salman Beg5y ago
Hey either you can use addrange method or concat method. Check this link for example, https://stackoverflow.com/questions/1528171/joining-two-lists-together