C # - how to sort a list of strings using the last character, ignoring special character if there is one at the end
Below is the logic I was trying to implement and able to sort it, but needs to figure out to ignore special characters in it.
My logic:
- Reversed string in a list
- Sorted ascending
- Sorted lines flipped back again &
-
Finally, it is returned as a string, appended to the ~ separator.
List<String> inputLst= new List<String>() { "Bananas!", "Cherry2", "Mango","Apples", "Grape$", "Guava" }; List<String> sortList = new List<String>(); List<String> outputList = new List<String>(); foreach (String str in inputLst) { sortList.Add(new String(str.ToCharArray().Reverse().ToArray())); } sortList.Sort(); foreach (String str in sortList) { outputList.Add(new String(str.ToCharArray().Reverse().ToArray())); } Return String.Join("~", outputList);
The conclusion I received Bananas!~Grape$~Cherry2~Guava~Mango~Apples
The expected result should be Guava~Grape$~Mango~Bananas!~Apples~Cherry2
Can anyone suggest me an optimized solution for sorting a list by the last character while ignoring special characters? Here I have used 2 lists to expand the lines, can this be done in a more efficient way? Note: without using LINQ PLS.
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With a bit of LINQ and Regex, this can be done relatively simply:
var inputList = new List<string>() { "Bananas!", "Cherry2", "Mango","Apples", "Grape$", "Guava" };
var outputList = inputList.OrderBy(s => new string(Regex.Replace(s, "[^a-zA-Z]", "")
.Reverse()
.ToArray()))
.ToList();
var output = String.Join("~", outputList);
EDIT: A non-LINQ approach:
var inputList = new List<string>() { "Bananas!", "Cherry2", "Mango", "Apples", "Grape$", "Guava" };
inputList.Sort(new ReverseStringComparer());
var output = String.Join("~", inputList);
ReverseStringComparer:
class ReverseStringComparer : IComparer<string>
{
public int Compare(string x, string y)
{
string a = new string(Regex.Replace(x, "[^a-zA-Z]", "").Reverse().ToArray());
string b = new string(Regex.Replace(y, "[^a-zA-Z]", "").Reverse().ToArray());
return a.CompareTo(b);
}
}
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Solution without regex:
string foo()
{
List<String> inputLst= new List<String>() { "Bananas!", "Cherry2", "Mango","Apples", "Grape$", "Guava" };
inputLst.Sort((l, r) => new string(l.Reverse().SkipWhile( x => !char.IsLetter(x) ).ToArray()).CompareTo( new string(r.Reverse().SkipWhile(x => !char.IsLetter(x)).ToArray()) ) );
return String.Join("~", inputLst);
}
To skip all non-letter characters (and not just at the beginning of a line), as suggested in the comment, simply use Where
instead SkipWhile
like this:
string bar()
{
List<String> inputLst= new List<String>() { "Bananas!", "Cherry2", "Mango","Apples", "Grape$", "Guava" };
inputLst.Sort((l, r) => new string(l.Reverse().Where( x => char.IsLetter(x) ).ToArray()).CompareTo( new string(r.Reverse().Where(x => char.IsLetter(x)).ToArray()) ) );
return String.Join("~", inputLst);
}
Note Where
has logic for queries ( char.IsLetter(x)
) versus SkipWhile
( !char.IsLetter(x)
).
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Find the last character that is a letter and sort it.
var inputList = new List<string>() {
"Bananas!", "Cherry2", "Mango","Apples", "Grape$", "Guava" };
var outputList = inputList.OrderBy(s => s.Last(c => char.IsLetter(c)));
Console.WriteLine(string.Join("~", outputList));
No reverse required.
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