Remove all characters after the last letter

Question

The following simple program will find the last letter in a string that a user enters and then remove everything after that point. So, if a person enters one string.... everything after the g should be removed. I've got the following as a little program:

class Program
{
    static void Main(string[] args)
    {
        Console.Write("Enter in the value of the string: ");
        List<char> charList = Console.ReadLine().Trim().ToList();

        int x = charList.LastIndexOf(charList.Last(char.IsLetter)) ;
        Console.WriteLine("this is the last letter {0}", x);
        Console.WriteLine("This is the length of the string {0}", charList.Count);
        Console.WriteLine("We should have the last {0} characters removed", charList.Count - x);

        for (int i = x; i < charList.Count; i++)
        {
            charList.Remove(charList[i]);
        }

        foreach (char c in charList)
        {
            Console.Write(c);
        }
        Console.ReadLine();
    }
}

I've tried numerous variations of this and none of them getting it exactly write. This particular program with an input of string.... the output of the program is strin.. So somehow it's leaving on what it should be taking away and it's actually taking away letters that it shouldn't. Can anyone give an indication as to why this is happening? The desired output, again should be string.

Answer 1

Try this:

string input = Console.ReadLine();                // ABC.ABC.
int index = input.Select((c, i) => new { c, i })
                 .Where(x => char.IsLetter(x.c))
                 .Max(x => x.i);
string trimmedInput = input.Substring(0, index + 1);
Console.WriteLine(trimmedInput);                  // ABC.ABC

Answer 2

Jsut for the explanation, that's because each time you remove a character, you increment the i counter but also decrementing charList.Count so you're actually removing 1 character, leaving the next one, then removing again and so on...

For example, with the input "string...." and x being 5 (index of the G letter) you're doing :

1st iteration : Remove the g char so x becomes 6 and charList.Count becomes 9 (10-1)

Next iteration : Remove the char at index 6 which is now the second . (your string being "strin....").

So you missed the first point.

I let you check other answers as they contains more elegant solutions for your problems.

Answer 3

I think it would be a lot more straight forward to simply Substring the string the user entered. So consider the following modified code:

 class Program
 {
    static void Main(string[] args)
    {
        Console.Write("Enter in the value of the string: ");
        var s = Console.ReadLine().Trim();
        List<char> charList = s.ToList();

        int x = charList.LastIndexOf(charList.Last(char.IsLetter)) ;
        Console.WriteLine("this is the last letter {0}", x);
        Console.WriteLine("This is the length of the string {0}", charList.Count);
        Console.WriteLine("We should have the last {0} characters removed", charList.Count - x);

        Console.WriteLine(s.Substring(0, x + 1);
        Console.ReadLine();
    }
}

here we store the value the user entered into s, find the last index of a letter, and then Substring through that letter when writing out to the console.

Answer 4

string s = console.ReadLine();
s = s.Substring(0, s.ToList().FindLastIndex(char.IsLetter) + 1);

Answer 5

You also can use a function of string called SubString, to get everything from the first to the last letter index.

Answer 6

Here's a pretty inefficient way to do it (just for fun!)

var trimmedInput = string.Join("", input.Reverse().SkipWhile(x => !char.IsLetter(x)).Reverse());

Answer 7

You could use this extension:

public static string TrimLettersLeft(this string input)
{ 
    int lastLetterIndex = -1;
    for (int i = input.Length - 1; i >= 0; i--)
    {
        if (Char.IsLetter(input[i]))
        {
            lastLetterIndex = i;
            break;
        }
    }

    if( lastLetterIndex == -1)
        return input;
    else
        return input.Substring(0, lastLetterIndex + 1);
}

Input: test...abc... Output: test...abc

DEMO

Answer 8

Solution will be like this.

string charList = "string..."; //any string place here
int x = charList.LastIndexOf(charList.Last(char.IsLetter));
String str = charList.ToString().Substring(0, x + 1);

Answer 9

This will match every word character (A-Z, 0-9 and _):

string Input = Console.ReadLine();
string Userinput = String.Empty;
Regex TextSearch = new Regex(@"\w*");

if(TextSearch.IsMatch(Input))
    Userinput = TextSearch.Match(Input).Groups[0].Value;
else
    // No valid Input

Answer 10

What I believe would be the shortest, simplest option:

Edit: A comment pointed out an initial error here, so I added a little fix. Should work nicely now (might not be the optimal solution, but I thought it was a fun an simple solution anyway):

var userInput = Console.ReadLine();

Console.WriteLine(new string(userInput.Reverse()
                                      .SkipWhile(c => !char.IsLetter(c))
                                      .Reverse()
                                      .ToArray()));