I wanted to match the words in string with reverse order.
We wanted to put validation to prompt user, if name exists in reverse order.
For example:
If name column has the value, 'Viral,Tennis'
Now if user enters a new name with the value, 'Tennis,Viral'
Then how can we match reverse order of word using regex or some other way?
I am using C#.net for development.
You could take a look at the Regex.Split(String input, String regex) and do something like so:
String[] userEntry = Regex.Split(userString, "\\s+");
StringBuilder sb = new StringBuilder()
for (int i = userEntry.Length -1; i >= 0; i--)
{
sb.append(userEntry[i]).append(" ");
}
String result = sb.ToString();
//Do Validation
That would do the trick, however, you need to keep in mind that things will get a little bit messy if you do not want to change the order of special symbols such as the comma. You could easily remove those and do any validation without special symbols.
EDIT: It depends on what you mean by special symbols. The regex [^a-zA-z0-9]+ will match any character which is not a letter (upper or lower case) and which is also not a number. So you could easily do something like so:
string input = ...
string pattern = "[^a-zA-z0-9]+";
string replacement = "";
Regex rgx = new Regex(pattern);
string result = rgx.Replace(input, replacement);
The above should yield a string which is only made from letters and digits. White spaces will also be removed.
Related
I want to check if a string only contains:
Letters
Numbers
Underscores
Periods
in Flutter, I tried the following to get only the letters but even if other characters are there it returns true if it contains a letter:
String mainString = "abc123";
print(mainString.contains(new RegExp(r'[a-z]')));
As I told it returns true since it contains letters, but I want to know if it only contains letters.
Is there a way to do that?
The problem with your RegExp is that you allow it to match substrings, and you match only a single character. You can force it to require that the entire string be matched with ^ and $, and you can match against one or more of the expression with +:
print(RegExp(r'^[a-z]+$').hasMatch(mainString));
To match all the characters you mentioned:
print(RegExp(r'^[A-Za-z0-9_.]+$').hasMatch(mainString));
the basic way of doing this is as follow:
define a list of acceptable characters:
// for example
List<String> validChar = ["1", "2", "3", "t"];
loop through all character of your string and check its validity:
// given text
String x = "t5";
bool valid = true;
for(int i=0; i<x.length; i++){
if(!validChar.contains(x[i])){
valid = false;
}
}
print(valid);
just change the x and validChar as your need.
I tried looking for an answer to this question but just couldn't finding anything and I hope that there's an easy solution for this. I have and using the following code in C#,
String pattern = ("(hello|hello world)");
Regex regex = new Regex(pattern, RegexOptions.IgnoreCase);
var matches = regex.Matches("hello world");
Question is, is there a way for the matches method to return the longest pattern first? In this case, I want to get "hello world" as my match as opposed to just "hello". This is just an example but my pattern list consist of decent amount of words in it.
If you already know the lengths of the words beforehand, then put the longest first. For example:
String pattern = ("(hello world|hello)");
The longest will be matched first. If you don't know the lengths beforehand, this isn't possible.
An alternative approach would be to store all the matches in an array/hash/list and pick the longest one manually, using the language's built-in functions.
Regular expressions (will try) to match patterns from left to right. If you want to make sure you get the longest possible match first, you'll need to change the order of your patterns. The leftmost pattern is tried first. If a match is found against that pattern, the regular expression engine will attempt to match the rest of the pattern against the rest of the string; the next pattern will be tried only if no match can be found.
String pattern = ("(hello world|hello wor|hello)");
Make two different regex matches. The first will match your longer option, and if that does not work, the second will match your shorter option.
string input = "hello world";
string patternFull = "hello world";
Regex regexFull = new Regex(patternFull, RegexOptions.IgnoreCase);
var matches = regexFull.Matches(input);
if (matches.Count == 0)
{
string patternShort = "hello";
Regex regexShort = new Regex(patternShort, RegexOptions.IgnoreCase);
matches = regexShort.Matches(input);
}
At the end, matches will be be the output of "full" or "short", but "full" will be checked first and will short-circuit if it is true.
You can wrap the logic in a function if you plan on calling it many times. This is something I came up with (but there are plenty of other ways you can do this).
public bool HasRegexMatchInOrder(string input, params string[] patterns)
{
foreach (var pattern in patterns)
{
Regex regex = new Regex(pattern, RegexOptions.IgnoreCase);
if (regex.IsMatch(input))
{
return true;
}
}
return false;
}
string input = "hello world";
bool hasAMatch = HasRegexMatchInOrder(input, "hello world", "hello", ...);
Is there a way to escape the special characters in regex, such as []()* and others, from a string?
Basically, I'm asking the user to input a string, and I want to be able to search in the database using regex. Some of the issues I ran into are too many)'s or [x-y] range in reverse order, etc.
So what I want to do is write a function to do replace on the user input. For example, replacing ( with \(, replacing [ with \[
Is there a built-in function for regex to do so? And if I have to write a function from scratch, is there a way to account all characters easily instead of writing the replace statement one by one?
I'm writing my program in C# using Visual Studio 2010
You can use .NET's built in Regex.Escape for this. Copied from Microsoft's example:
string pattern = Regex.Escape("[") + "(.*?)]";
string input = "The animal [what kind?] was visible [by whom?] from the window.";
MatchCollection matches = Regex.Matches(input, pattern);
int commentNumber = 0;
Console.WriteLine("{0} produces the following matches:", pattern);
foreach (Match match in matches)
Console.WriteLine(" {0}: {1}", ++commentNumber, match.Value);
// This example displays the following output:
// \[(.*?)] produces the following matches:
// 1: [what kind?]
// 2: [by whom?]
you can use Regex.Escape for the user's input
string matches = "[]()*";
StringBuilder sMatches = new StringBuilder();
StringBuilder regexPattern = new StringBuilder();
for(int i=0; i<matches.Length; i++)
sMatches.Append(Regex.Escape(matches[i].ToString()));
regexPattern.AppendFormat("[{0}]+", sMatches.ToString());
Regex regex = new Regex(regexPattern.ToString());
foreach(var m in regex.Matches("ADBSDFS[]()*asdfad"))
Console.WriteLine("Found: " + m.Value);
I want to place a dash after every letter but my regex place a dash at the end too. How can I improve my regex?
String outputS = dnaString.replaceAll("(.{1})", "$1-");
(.)(?!$)
You can use this.Replace by $1.See demo.
https://regex101.com/r/gT6vU5/11
(?!$) uses negative lookahead to state that do not capture a character which is at end of string.
Without regex (that is faster):
String[] nucleotides = dnaString.split("");
String outputS;
int seqLength = nucleotides.length;
if (seqLength > 1) {
StringBuilder sb = new StringBuilder();
sb.append(nucleotides[0]);
for (int i = 1; i < seqLength; i++) {
sb.append("-");
sb.append(nucleotides[i]);
}
outputS = sb.toString();
} else {
outputS = dnaString;
}
I know this is an old question, but for completeness and future reference I would like to add this answer.
In Java 8 you can also use:
String.join("-",dnaString.toCharArray());
Explanation:
String.join(delimiter,objects...);
String.join(delimiter,array);
String.join(delimiter,Iterable);
These are used to join all objects to a single string with the delimiter as separator.
dnaString.toCharArray();
This is a method to get a String as an char array.
This replaces all special characters with underscore '_' except the last occurence of a special character in the string.
String name = "one-of-the dummy$ string:i.txt"; // input
name = name.replaceAll("[^a-zA-Z0-9](?=.*[^a-zA-Z0-9])", "_");
System.out.println(name);
//input: one-of-the dummy$ string:i.txt
//output: one_of_the_dummy__string_i.txt
This
(.)\B
doesn't match the last char.
See https://regex101.com/r/p0Z0zA/1
So, in your case, should be:
String outputS = dnaString.replaceAll("(.{1})\\B", "$1-");
Credits to pigreco.
I am writing a function to format a string. I receive a string of numbers, sometimes with dashes, sometimes not. I need to produce an output string of 14 characters, so if the input string contains less than 14, I need to pad it with zeros. then I need to mask the string of numbers by inserting dashes in appropriate places. Here is what I got so far:
strTemp = strTemp.Replace("-", "")
If IsNumeric(strTemp) Then
If strTemp.Length < 14 Then
strTemp = strTemp.PadRight(14 - strTemp.Length)
End If
output = String.Format(strTemp, "{00-000-0-0000-00-00}")
End If
The above works fine, except it just returns a string of numbers without putting in the dashes. I know I am doing something wrong with String.Format but so far I've only worked with pre-defined formats. Can anyone help? How can I use Regex for string formatting in this case?
This function should do the trick:
Public Function MaskFormat(input As String) As String
input = input.Replace("-", String.Empty)
If IsNumeric(input) Then
If input.Length < 14 Then
input = input.PadRight(14 - input.Length)
End If
Return String.Format("{0:00-000-0-0000-00-00}", CLng(input))
Else
Return String.Empty
End If
End Function
You can find more on String formatting here.