Reputation: 662
I would like to remove the duplicate elements from a List. Some elements of the list looks like this:
Book 23
Book 22
Book 19
Notebook 22
Notebook 19
Pen 23
Pen 22
Pen 19
To get rid of duplicate elements i've done this:
List<String> nodup = dup.Distinct().ToList();
I would like to keep in the list just
Book 23
Notebook 22
Pen 23
How can i do that ?
Upvotes: 2
Views: 6789
Reputation: 758
a bit old fashioned , but it should work , If I understand correctrly
Dictionary<string,int> dict=new Dictionary<string,int>();
//Split accepts 1 character ,assume each line containes key value pair seperated with spaces and not containing whitespaces
input=input.Replace("\r\n","\n");
string[] lines=input.Split('\n');
//break to categories and find largest number at each
foreach(line in lines)
{
string parts[]=line.Split(' ');
string key=parts[0].Trim();
int value=Convert.ToInt32(parts[1].Trim());
if (dict.ContainsKey(key))
{
dict.Add(key, value);
}
else
{
if (dict[key]<value)
{
dict[key]=value;
}
}
}
//do somethig with dict
Upvotes: 0
Reputation: 460370
You can use LINQ
in combination with some String
operations to group all your itemy by name and MAX(Number)
:
var q = from str in list
let Parts = str.Split(new char[] { ' ' }, StringSplitOptions.RemoveEmptyEntries)
let item = Parts[ 0 ]
let num = int.Parse(Parts[ 1 ])
group new { Name = item, Number = num } by item into Grp
select new {
Name = Grp.Key,
Value = Grp.Max(i => i.Number).ToString()
};
var highestGroups = q.Select(g =>
String.Format("{0} {1}", g.Name, g.Value)).ToList();
(Same as Reed's approach but in query syntax which is better readable to my mind)
Edit: I cannot reproduce your comment that it does not work, here is sample data:
List<String> list = new List<String>();
list.Add("Book 23");
list.Add("Book 22");
list.Add("Book 19");
list.Add("Notebook 23");
list.Add("Notebook 22");
list.Add("Notebook 19");
list.Add("Pen 23");
list.Add("Pen 22");
list.Add("Pen 19");
list.Add("sheet 3");
var q = from str in list
let Parts = str.Split(new char[] { ' ' }, StringSplitOptions.RemoveEmptyEntries)
let item = Parts[ 0 ]
let num = int.Parse(Parts[ 1 ])
group new { Name = item, Number = num } by item into Grp
select new {
Name = Grp.Key,
Value = Grp.Max(i => i.Number).ToString()
};
var highestGroups = q.Select(g => String.Format("{0} {1}", g.Name, g.Value));
MessageBox.Show(String.Join(Environment.NewLine, highestGroups));
The result:
Book 23
Notebook 23
Pen 23
sheet 3
Upvotes: 2
Reputation: 12521
You may want to add a custom comparer as a parameter, as you can see in the example on MSDN.
In this example I assumed Foo
is a class with two members.
class Program
{
static void Main(string[] args)
{
var list = new List<Foo>()
{
new Foo("Book", 23),
new Foo("Book", 22),
new Foo("Book", 19)
};
foreach(var element in list.Distinct(new Comparer()))
{
Console.WriteLine(element.Type + " " + element.Value);
}
}
}
public class Foo
{
public Foo(string type, int value)
{
this.Type = type;
this.Value = value;
}
public string Type { get; private set; }
public int Value { get; private set; }
}
public class Comparer : IEqualityComparer<Foo>
{
public bool Equals(Foo x, Foo y)
{
if(x == null || y == null)
return x == y;
else
return x.Type == y.Type;
}
public int GetHashCode(Foo obj)
{
return obj.Type.GetHashCode();
}
}
This works on an IList
, assuming that we want the first item each, not the one with the highest number. Be careful with different collection types (like ICollection
or IEnumerable
), as they do not guarantee you any order. Therefore any of the Foo
s may remain after the Distinct
.
You could also override both Equals
and GetHashCode
of Foo
instead of using a custom IEqualityComparer
. However, I would not actually recommend this for a local distinct. Consumers of your class may not recognize that two instances with same value for Type
are always equal, regardless of their Value
.
Upvotes: 1
Reputation: 564931
It's not 100% clear what you want here - however...
If you want to keep the "largest" number in the list, you could do:
List<string> noDup = dup.Select(s => s.Split(new[] {' '}, StringSplitOptions.RemoveEmptyEntries)
.Select(p => new { Name=p[0], Val=int.Parse(p[1]) })
.GroupBy(p => p.Name)
.Select(g => string.Join(" ", g.Key, g.Max().ToString()))
.ToList();
This would transform the List<string>
by parsing the numeric portion into a number, taking the max per item, and creating the output string as you have specified.
Upvotes: 3
Reputation: 825
you can do someting like
string firstElement = dup.Distinct().ToList().First();
and add it to another list if you want.
Upvotes: 3