I have two lists like below in C#.
List 1 = [{Item="A",position =1},{Item="B",position =2},{Item="A",position =3}]
List 2 = [{Item="AA",position =1},{Item="BB",position =2},{Item="AC",position =3}]
Now i want to remove duplicate values in the List 1 and that position should be removed in the List 2.
Example o/p
List 1 = [{Item="A",position =1},{Item="B",position =2}]
List 2 = [{Item="AA",position =1},{Item="BB",position =2}]
Can any one help me. Thanks.
List<string> lst1 = new List<string> { "A", "B", "A" };
List<string> lst2 = new List<string> { "AA", "BB", "AC" };
HashSet<string> seen = new HashSet<string>();
for (int i = 0; i < lst1.Count; i++) {
if (!seen.Add(lst1[i])) {
lst1.RemoveAt(i);
lst2.RemoveAt(i);
i--;
}
}
I used a HashSet to "save" the "already seen" elements of lst1 and then simply cycle the lst1 and remove the duplicate elements. HashSet.Add returns true if the HashSet doesn't already have an element, false if it already has it.
It isn't exactly clear what you want/what you have, but here there is the solution for another possible use case:
public class MyObject {
public string Item;
public int Position;
}
List<MyObject> lst1 = new List<MyObject> {
new MyObject { Item = "A", Position = 1 },
new MyObject { Item = "B", Position = 2 },
new MyObject { Item = "A", Position = 3 },
};
List<MyObject> lst2 = new List<MyObject> {
new MyObject { Item = "AA", Position = 1 },
new MyObject { Item = "BB", Position = 2 },
new MyObject { Item = "AC", Position = 3 },
};
HashSet<string> seen = new HashSet<string>();
HashSet<int> toBeDeleted = new HashSet<int>();
for (int i = 0; i < lst1.Count; i++) {
if (!seen.Add(lst1[i].Item)) {
toBeDeleted.Add(lst1[i].Position);
lst1.RemoveAt(i);
i--;
}
}
if (toBeDeleted.Count > 0) {
for (int i = 0; i < lst2.Count; i++) {
if (toBeDeleted.Contains(lst2[i].Position)) {
lst2.RemoveAt(i);
i--;
}
}
// or equivalent and shorter, without the for cycle
//lst2.RemoveAll(x => toBeDeleted.Contains(x.Position));
}
In this case in a first pass on lst1 we remove the duplicate items (as seen in the first example) and "save" the Positions that need to be deleted in the HashSet<int> tobedeleted and then we do a second pass on lst2 to remove the elements that need deleting.
Much not clear what you want do, but I try with this:
var filteredList1 = list1.GroupBy(x => x.Item).Select(g => g.First()).ToList();
var removeElements = list2.Where(f => !filteredList1.Any(t => t.Position == f.Position)).ToList();
removeElements.ForEach(x => list2.Remove(x));
Related
I'm facing an issue while displaying multiple lists the value in a single row column.
Here is an example of code.
public class Program
{
static void Main(string[] args)
{
Dictionary<string, List<object>> keyvalues = new Dictionary<string, List<object>>();
keyvalues.Add("Code", new List<object>() { 1, 2, 3, 4 });
keyvalues.Add("Name", new List<object>() { "A", "B", "C", "D" });
keyvalues.Add("Age", new List<object>() { 20, 30, 40, 50 });
var listData = keyvalues.Select(x => x.Value).Select((x, i) => new { obj = x, index = i });
var listData = keyvalues.Select((x, iparent) => x.Value.Select((z, i) => new { value = string.Concat(z, x.Value[i]) }).ToList()).ToList();
Console.ReadLine();
}
}
Expected output
1A20
2B30
3C40
4D50
If you are using .Net 6, you could make use of the new 3 way Zip extension.
var result = keyvalues["Code"].Zip(keyvalues["Name"], keyvalues["Age"])
.Select(x=> $"{x.First}{x.Second}{x.Third}");
Why make it so complicated?
for(int x = 0; x<keyValues["Code"].Count; x++)
Console.WriteLine(
keyValues["Code"][x]+
keyValues["Name"][x]+
keyValues["Age"][x]
);
LINQ's a hammer; not every problem is a nail.
ps if you have N keys, you can easily turn it into a
var keys = new[]{"Code","Name","Age","Foo","Bar"};
for(...)
foreach(var k in keys)
... //some concat here or use the values directly eg adding to your page
You could easily use Zip here. However, you could roll your own
public static IEnumerable<string> DoStuff<T, T2>(Dictionary<T, List<T2>> source)
{
var max = source.Values.Max(x => x?.Count ?? 0);
for (var i = 0; i < max; i++)
yield return string.Concat(source.Values.Select(x => x.ElementAtOrDefault(i)));
}
Usage
var results = DoStuff(keyvalues);
Console.WriteLine(string.Join(Environment.NewLine,results));
Output
1A20
2B30
3C40
4D50
or
public static IEnumerable<string> DoStuff<T>(List<T>[] source)
{
var max = source.Max(x => x?.Count ?? 0);
for (var i = 0; i < max; i++)
yield return string.Concat(source.Select(x => x.ElementAtOrDefault(i)));
}
...
var results = DoStuff(keyvalues.Values.ToArray());
Console.WriteLine(string.Join(Environment.NewLine,results));
There is a similar question that doesn't answer my question. --> Count number of element in List>
I have a list which contains sublists:
List<string> sublist1 = new List<string>() { "a", "b" };
List<string> sublist2 = new List<string>() { "a", "b" };
List<string> sublist3 = new List<string>() { "a", "c" };
Now I want to count the occurrences of each list.
a, b --> 2
a, c --> 1
I used distinct() from LINQ, but I got the output:
a, b --> 1
a, b --> 1
a, c --> 1
I assume that the hashcode is different.
Is there an alternative to distinct() which is looking at the list values instead?
I want to solve this in LINQ if possible.
Edit:
The order of list items has to be the same!
To use GroupBy() to do this, you will need a suitable IEqualityComparer<List<string>> that compares lists of strings. There is no built-in implementation, so you have to roll your own:
public sealed class StringListEqualityComparer : IEqualityComparer<List<string>>
{
public bool Equals(List<string> x, List<string> y)
{
if (ReferenceEquals(x, y))
return true;
if (x == null || y == null)
return false;
return x.SequenceEqual(y);
}
public int GetHashCode(List<string> strings)
{
int hash = 17;
foreach (var s in strings)
{
unchecked
{
hash = hash * 23 + s?.GetHashCode() ?? 0;
}
}
return hash;
}
}
Once you've got that, you can use it with GroupBy() as follows:
public static void Main()
{
var sublist1 = new List<string>{ "a", "b" };
var sublist2 = new List<string>{ "a", "b" };
var sublist3 = new List<string>{ "a", "c" };
var listOfLists = new List<List<string>> {sublist1, sublist2, sublist3};
var groups = listOfLists.GroupBy(item => item, new StringListEqualityComparer());
foreach (var group in groups)
{
Console.WriteLine($"Group: {string.Join(", ", group.Key)}, Count: {group.Count()}");
}
}
public JsonResult CountList(){
List<List<string>> d = new List<List<string>>(); //SuperList
d.Add(new List<string> { "a", "b" }); //List 1
d.Add(new List<string> { "a", "b" }); // List 2
d.Add(new List<string> { "a", "c" }); // List 3
d.Add(new List<string> { "a", "c", "z" }); //List 4
var listCount = from items in d
group items by items.Aggregate((a,b)=>a+""+b) into groups
select new { groups.Key, Count = groups.Count() };
return new JsonResult(listCount);
}
This will give the following Result as output in Post Man or Advanced REST Client
[{
"key": "ab",
"count": 2
},
{
"key": "ac",
"count": 1
},
{
"key": "acz",
"count": 1
}],
I think this will be helpful
var list = new List<List<string>>() { sublist1, sublist2, sublist3};
var result = list.GroupBy(x => string.Join(",",x)).ToDictionary(x => x.Key.Split(',').ToList(), x => x.Count());
You can try the below code:-
List<string> sublist1 = new List<string>() { "a", "b" };
List<string> sublist2 = new List<string>() { "a", "b" };
List<string> sublist3 = new List<string>() { "a", "c" };
List<List<string>> listOfLists = new List<List<string>> { sublist1, sublist2, sublist3 };
Dictionary<string, int> counterDictionary = new Dictionary<string, int>();
foreach (List<string> strList in listOfLists)
{
string concat = strList.Aggregate((s1, s2) => s1 + ", " + s2);
if (!counterDictionary.ContainsKey(concat))
counterDictionary.Add(concat, 1);
else
counterDictionary[concat] = counterDictionary[concat] + 1;
}
foreach (KeyValuePair<string, int> keyValue in counterDictionary)
{
Console.WriteLine(keyValue.Key + "=>" + keyValue.Value);
}
I think I will solve this with:
var equallists = list1.SequenceEqual(list2);
Therefore I compare distinct lists and lists with SequenceEquals() and counting them.
Better solutions welcome. :)
Items is public list of MenuListItemViewModel items, in example below im creating new list with 2 elements:
Items = new List<MenuListItemViewModel>
{
new MenuListItemViewModel
{
Value = "500",
Letter = "D"
},
new MenuListItemViewModel
{
Value = "-500",
Letter = "W"
},
};
How to do exactly the same but with variable numbers of items i want to have in the list? Something like loop x times (like below, but it wont work in current state)
for (int i = 0; i < 5; i++)
{
new MenuListItemViewModel
{
Value = "500",
Letter = "D"
},
}
You can use LINQ:
Items = Enumerable.Range(0, number)
.Select(i => new MenuListItemViewModel
{
Value = "500",
Letter = "D"
}).ToList();
You can do
Items = new List<MenuListItemViewModel>();
for (int i = 0; i < 5; i++)
{
Items.Add(
new MenuListItemViewModel
{
Value = "500",
Letter = "D"
});
}
I have a problem with a list that I want to alter, before outputting it back to the client.
For the sake of the question I will post an example of the list and how I need to result to look, because I have looked at Intersect, Except and everything else I could think of, but didn't get the result I am looking for.
Example List:
1, 4, 6, 8
1, 2, 6, 8
2, 4, 6, 8
3, 4, 5, 7
Required Result:
1, 4, 6, 8 //Initial row
-, 2, -, - //Items that have not changed will show as a -
2, 4, -, -
3, -, 5, 7
I really hope I explained it well.
I would be happy to explain this further if needed.
Thanks in advance for the advice, so far I have wrecked my brain over this. ;)
What I tried is too much to type here, so here is what I have so far. Except simply won't do anything with the data because it thinks the rows are different, so they just stay the same.
private List<List<string>> FilterData(List<string[]> datatable)
{
List<string> previousRow = new List<string>();
List<string> currentRow = new List<string>();
List<string> rowDifferences = new List<string>();
List<List<string>> resultingDataset = new List<List<string>>();
foreach (var item in datatable)
{
if (previousRow == null)
{
previousRow = item.ToList();
continue;
}
currentRow = item.ToList();
rowDifferences = currentRow.Except(previousRow).ToList();
resultingDataset.Add(rowDifferences);
}
return resultingDataset;
}
Few things you have to change in your code;
Here is code:
private List<string[]> FilterData(List<string[]> datatable)
{
// List is made of String Array, so need string[] variable not list
string[] previousRow = null ;
string[] currentRow;
string[] rowDifferences ;
// to store the result
List<string[]> resultingDataset = new List<string[]>();
foreach (var item in datatable)
{
if (previousRow == null)
{
previousRow = item;
resultingDataset.Add(previousRow); // add first item to list
continue;
}
currentRow = item;
// check and replace with "-" if elment exist in previous
rowDifferences = currentRow.Select((x, i) => currentRow[i] == previousRow[i] ? "-" : currentRow[i]).ToArray();
resultingDataset.Add(rowDifferences);
// make current as previos
previousRow = item;
}
return resultingDataset;
}
check this dotnetfiddle
private static List<List<string>> FilterData(List<List<string>> datatable)
{
var result = new List<List<string>>();
for(var rowindex = 0; rowindex < datatable.Count; rowindex++)
{
// Clone the string list
var refrow = datatable[rowindex]
.Select(item => (string)item.Clone()).ToList();
result.Add(refrow);
// First row will not get modify anyway
if (rowindex == 0) continue;
var row = result[rowindex];
// previous row of result has changed to "-", so use the original row to compare
var prevrow = datatable[rowindex - 1];
for(var columnindex = 0; columnindex < row.Count; columnindex++)
{
if (row[columnindex] == prevrow[columnindex])
row[columnindex] = "-";
}
}
return result;
}
fiddle
public static List<List<T>> RemoveDuplicates<T>(this List<List<T>> items, T replacedValue) where T: class
{
List<List<T>> ret = items;
items.ForEach(m=> {
var ind = items.IndexOf(m);
if(ind==0)
{
ret.Add(items.FirstOrDefault());
}
else
{
var prevItem = items.Skip(items.IndexOf(m)-1).FirstOrDefault();
var item = new List<T>();
for(var a = 0; a < prevItem.Count; a++)
{
item.Add(prevItem[a] == m[a]? replacedValue : m[a]);
}
ret.Add(item);
}
});
return ret;
}
How to use it:
var items = new List<List<string>>{
new List<string>{ "1", "4", "6", "8" },
new List<string>{ "1", "2", "6", "8" },
new List<string>{ "2", "4", "6", "8" },
new List<string>{ "3", "4", "5", "7" }
};
var result = items.RemoveDuplicates("-");
dotNetFiddle: https://dotnetfiddle.net/n36p64
I have a List<string[]> parsedData.
I have another List<string[]> newData = {n, 1, 2, 3}.
The strings in parsedData seems to be stored the following way:
1. a b c
2. 1 2 3
3. 1 2 3
Which is perfect. When I add the newData to parsedData it becomes like this:
1. a b c
2. 1 2 3
3. 1 2 3
4. n 1 2 3
I'm searching for a way to transpose the newData list and add it in a similar fashion but I have problem getting it to work. Can someone please shed some light on this matter.
This is the code when I parse parsedData:
List<string[]> parsedData = new List<string[]>();
string[] fields;
try
{
TextFieldParser parser = new TextFieldParser(path);
parser.TextFieldType = FieldType.Delimited;
parser.SetDelimiters(",");
while (!parser.EndOfData)
{
fields = parser.ReadFields();
for (int i = 0; i < fields.Length; i++)
{
if (fields[i] == "NaN")
fields[i] = null;
}
parsedData.Add(fields);
}
parser.Close();
}
catch (Exception e)
{
MessageBox.Show(e.Message);
}
return parsedData;
The string[] newData is added to a list in this way:
List<string[]> newData = new List<string[]>();
string[] mCol = mean.meanCol(c, parsedData); // function that returns a string[]
newData.Add(mCol);
I then want to join the two lists as explained above so it looks like this:
a b c n
1 2 3 1
1 2 3 2
1 2 3 3
Okay, I assume you have a text file that looks something like this:
a,b,c
1,2,3
1,2,3
and after you read/parse it, you end up with something that is equal to:
List<string[]> parsedData =
new List<string[]>
{
new []{"a", "b", "c"},
new []{"1", "2", "3"},
new []{"1", "2", "3"}
};
and then you want to be able to add something like:
List<string[]> newData =
new List<string[]>
{
new []{"n", "1", "2", "3"},
new []{"m", "1", "2", "3"},
// ... added more new data
};
Well, first the newData is "turned" 90° and each item has one more data point than the existing ones (a has 1 and 1, while n has 1, 2 and 3).
So even in the ideal way, you'd end up with:
List<string[]> combinedData =
new List<string[]>
{
new []{"a", "b", "c", "n", "m"},
new []{"1", "2", "3", "1", "1"},
new []{"1", "2", "3", "2", "2"},
new []{null, null, null, "3", "3"}
};
And second, you use string[] instead of List<string>, so growing is more complicated.
In any case, a List<string[]> is a suboptimal data structure to express what you want: having several channel names and being able to store several measurements per channel name.
I'd suggest a Dictionary<string, List<string>>, where the key is the channel name and the value, which is a List<string> contains the list of measurements for that channel name.
There are probably easier ways to do it, but one way to get from your List<string[]> to a Dictionary<string, List<string>> could work like:
var transposedData = new Dictionary<string, List<string>>();
var minArrayLength = parsedData.Min(a => a.Length);
for (var index = 0; index < minArrayLength; index++)
{
string key = null;
foreach (var array in parsedData)
{
if (key == null)
{
key = array[index];
transposedData[key] = new List<string>();
}
else
{
transposedData[key].Add(array[index]);
}
}
}
Btw. don't get confused by the var keyword, I like to use that a lot.
Once you have it in this data structure, you can add your newData like this:
foreach (var array in newData)
{
var key = array[0];
transposedData[key] = new List<string>();
// skip the key
for (var index = 1; index < array.Length; index++)
{
transposedData[key].Add(array[index]);
}
}
Now, the question is, are you happy with that, or do you really need a List<string[]> again? If so, you need to transpose it back. Maybe with something like this:
// using a list inside for now for easier adding
var backTranspose = new List<List<string>>();
// determine the max number of measurements for a channel name
var maxLength = transposedData.Values.Max(l => l.Count);
// use one more to include key
for (var valueIndex = 0; valueIndex <= maxLength; valueIndex++)
{
backTranspose.Add(new List<string>());
}
foreach (var kvp in transposedData)
{
var index = 0;
backTranspose[index].Add(kvp.Key);
for (var valueIndex = 0; valueIndex < maxLength; valueIndex++)
{
index++;
if (kvp.Value.Count > valueIndex)
{
backTranspose[index].Add(kvp.Value[valueIndex]);
}
else
{
backTranspose[index].Add(null);
}
}
}
// turn the lists back into arrays
parsedData = new List<string[]>();
foreach (var list in backTranspose)
{
parsedData.Add(list.ToArray());
}
One caveat though, a Dictionary is not ordered. So you might end up with channel names at different positions. But of course, the channel name and the corresponding measurement data will have the same index.
You can use LINQ and Concat to achieve what you need to do.
var allData = parsedData.Concat( newData ).ToList();