trim last character if not a number

Question

I'm trying to trim out the last charater from a string if not a number For example : "2+3-4*" From there last astrik needs to be trimmed as it is not a number my result should be as "2+3-4". If user enters "2+3+8" then no needs to trim as the last is number.

Answer 1

You can use this regex: [^0-9]$ to determine if the last character is something other than a number. If the regex is a match, simply remove the last character.

string a = "abc";
if (Regex.IsMatch(a, "[^0-9]$"))
{
  a = a.Remove(a.Length - 1);
}

Answer 2

You can check the last char is numeric or not using below snippet:

eg:

string value = "4+8-4*";
int outInt = 0;
bool isLastCharNumeric = int.TryParse(value[value.Length - 1].ToString(), out outInt);
if (!isLastCharNumeric)
{
    //chop off the last char
    value = value.Remove(value.Length - 1;);
}

Answer 3

You could grab the last character and check if it is a number then remove if so.

string str = "2+3-4*";

if(!Char.IsNumber(str[str.Length - 1])){
  str = str.Remove(str.Length - 1);
}

Answer 4

Use Regex:

string str= "2+3-4*";
str = Regex.Replace(str, "[^0-9]$", "");

Answer 5

Probably you can use a regular expression:

string input = "2+3+";
// Regexp => one or more occurences of a non-numeric character at
// the end of the string
string santizedInput = Regex.Replace(input, "[^0-9]+$", "");

Answer 6

I would use a regular expression. [^\d]+$

See the results: https://regex101.com/r/pE0h48/1

Answer 7

I think regex would be a good clean way to address this.

Regex rgx = new Regex("\D+$");
string result = rgx.Replace("2+3-4*", "");

Answer 8

My approach would be using a regular expression, but instead of using it to replace the last character, I would use the regular expression to extract the valid part of the string. My approach is coded in Java, but you can very easily translate it to C#.

Pattern pattern = Pattern.compile("([0-9]+)([\\+\\-\\:\\*][0-9])+");
Matcher m;
String input = "++2+4+5-6*3+4*2-3--";
m = pattern.matcher(input);
while(m.find()){
    System.out.println(m.group());
}

Answer 9

I'm not big on regular expressions as they're pretty slow, relatively speaking. We can solve this pretty easily by defining what numbers are and then just checking to see if the last character is one of them. So first lets open by specifying what we consider to be numbers.

static readonly char[] numbers = new char[] { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9' };

Now we need to return one of two results depending on whether or not our last character is one of the characters we just listed. To accomplish this lets use a ternary statement.

var testInput = "testing5";//Testing input
var trimmedString = 
    numbers.Any(x => x == testInput[testInput.Length - 1]) ?//testInput.Length - 1 is going to give us the last character in the string
    testInput : //It's a number so go ahead and return the full string
    testInput.SubString(0, testInput.Length - 1);//It's not a number so lets return all but the last character in the string as a new string.

So our final product looks like this. I encapsulated it into a method since it's a pretty self contained aspect of your code (presumably).

static readonly char[] numbers = new char[] { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9' };

public static string TrimNonNumbers(string input)
{
    if (string.IsNullOrEmpty(input)) return input;//Our math will produce an index out of range exception with an empty string.  So this is a safety to prevent that.
    return numbers.Any(x => x == testInput[testInput.Length - 1]) ? testInput : testInput.SubString(0, testInput.Length - 1);
}

Answer 10

Working, tested code

using System;

public class Program
{
    public static void Main()
    {
        string calculation = "2+3+81%";
        int length = calculation.Length;
        if(!Char.IsNumber(calculation[length-1])){
            calculation = calculation.TrimEnd(calculation[length-1]);
        }
        Console.Write(calculation);
    }
}