Related
I have a requirement to find and extract a number contained within a string.
For example, from these strings:
string test = "1 test"
string test1 = " 1 test"
string test2 = "test 99"
How can I do this?
\d+ is the regex for an integer number. So
//System.Text.RegularExpressions.Regex
resultString = Regex.Match(subjectString, #"\d+").Value;
returns a string containing the first occurrence of a number in subjectString.
Int32.Parse(resultString) will then give you the number.
Here's how I cleanse phone numbers to get the digits only:
string numericPhone = new String(phone.Where(Char.IsDigit).ToArray());
go through the string and use Char.IsDigit
string a = "str123";
string b = string.Empty;
int val;
for (int i=0; i< a.Length; i++)
{
if (Char.IsDigit(a[i]))
b += a[i];
}
if (b.Length>0)
val = int.Parse(b);
use regular expression ...
Regex re = new Regex(#"\d+");
Match m = re.Match("test 66");
if (m.Success)
{
Console.WriteLine(string.Format("RegEx found " + m.Value + " at position " + m.Index.ToString()));
}
else
{
Console.WriteLine("You didn't enter a string containing a number!");
}
What I use to get Phone Numbers without any punctuation...
var phone = "(787) 763-6511";
string.Join("", phone.ToCharArray().Where(Char.IsDigit));
// result: 7877636511
Regex.Split can extract numbers from strings. You get all the numbers that are found in a string.
string input = "There are 4 numbers in this string: 40, 30, and 10.";
// Split on one or more non-digit characters.
string[] numbers = Regex.Split(input, #"\D+");
foreach (string value in numbers)
{
if (!string.IsNullOrEmpty(value))
{
int i = int.Parse(value);
Console.WriteLine("Number: {0}", i);
}
}
Output:
Number: 4
Number: 40
Number: 30
Number: 10
if the number has a decimal points, you can use below
using System;
using System.Text.RegularExpressions;
namespace Rextester
{
public class Program
{
public static void Main(string[] args)
{
//Your code goes here
Console.WriteLine(Regex.Match("anything 876.8 anything", #"\d+\.*\d*").Value);
Console.WriteLine(Regex.Match("anything 876 anything", #"\d+\.*\d*").Value);
Console.WriteLine(Regex.Match("$876435", #"\d+\.*\d*").Value);
Console.WriteLine(Regex.Match("$876.435", #"\d+\.*\d*").Value);
}
}
}
results :
"anything 876.8 anything" ==> 876.8
"anything 876 anything" ==> 876
"$876435" ==> 876435
"$876.435" ==> 876.435
Sample : https://dotnetfiddle.net/IrtqVt
Here's a Linq version:
string s = "123iuow45ss";
var getNumbers = (from t in s
where char.IsDigit(t)
select t).ToArray();
Console.WriteLine(new string(getNumbers));
Another simple solution using Regex
You should need to use this
using System.Text.RegularExpressions;
and the code is
string var = "Hello3453232wor705Ld";
string mystr = Regex.Replace(var, #"\d", "");
string mynumber = Regex.Replace(var, #"\D", "");
Console.WriteLine(mystr);
Console.WriteLine(mynumber);
You can also try this
string.Join(null,System.Text.RegularExpressions.Regex.Split(expr, "[^\\d]"));
Here is another Linq approach which extracts the first number out of a string.
string input = "123 foo 456";
int result = 0;
bool success = int.TryParse(new string(input
.SkipWhile(x => !char.IsDigit(x))
.TakeWhile(x => char.IsDigit(x))
.ToArray()), out result);
Examples:
string input = "123 foo 456"; // 123
string input = "foo 456"; // 456
string input = "123 foo"; // 123
Just use a RegEx to match the string, then convert:
Match match = Regex.Match(test , #"(\d+)");
if (match.Success) {
return int.Parse(match.Groups[1].Value);
}
string input = "Hello 20, I am 30 and he is 40";
var numbers = Regex.Matches(input, #"\d+").OfType<Match>().Select(m => int.Parse(m.Value)).ToArray();
You can do this using String property like below:
return new String(input.Where(Char.IsDigit).ToArray());
which gives only number from string.
For those who want decimal number from a string with Regex in TWO line:
decimal result = 0;
decimal.TryParse(Regex.Match(s, #"\d+").Value, out result);
Same thing applys to float, long, etc...
var match=Regex.Match(#"a99b",#"\d+");
if(match.Success)
{
int val;
if(int.TryParse(match.Value,out val))
{
//val is set
}
}
The question doesn't explicitly state that you just want the characters 0 to 9 but it wouldn't be a stretch to believe that is true from your example set and comments. So here is the code that does that.
string digitsOnly = String.Empty;
foreach (char c in s)
{
// Do not use IsDigit as it will include more than the characters 0 through to 9
if (c >= '0' && c <= '9') digitsOnly += c;
}
Why you don't want to use Char.IsDigit() - Numbers include characters such as fractions, subscripts, superscripts, Roman numerals, currency numerators, encircled numbers, and script-specific digits.
Here is another simple solution using Linq which extracts only the numeric values from a string.
var numbers = string.Concat(stringInput.Where(char.IsNumber));
Example:
var numbers = string.Concat("(787) 763-6511".Where(char.IsNumber));
Gives: "7877636511"
var outputString = String.Join("", inputString.Where(Char.IsDigit));
Get all numbers in the string.
So if you use for examaple '1 plus 2' it will get '12'.
Extension method to get all positive numbers contained in a string:
public static List<long> Numbers(this string str)
{
var nums = new List<long>();
var start = -1;
for (int i = 0; i < str.Length; i++)
{
if (start < 0 && Char.IsDigit(str[i]))
{
start = i;
}
else if (start >= 0 && !Char.IsDigit(str[i]))
{
nums.Add(long.Parse(str.Substring(start, i - start)));
start = -1;
}
}
if (start >= 0)
nums.Add(long.Parse(str.Substring(start, str.Length - start)));
return nums;
}
If you want negative numbers as well simply modify this code to handle the minus sign (-)
Given this input:
"I was born in 1989, 27 years ago from now (2016)"
The resulting numbers list will be:
[1989, 27, 2016]
An interesting approach is provided here by Ahmad Mageed, uses Regex and StringBuilder to extract the integers in the order in which they appear in the string.
An example using Regex.Split based on the post by Ahmad Mageed is as follows:
var dateText = "MARCH-14-Tue";
string splitPattern = #"[^\d]";
string[] result = Regex.Split(dateText, splitPattern);
var finalresult = string.Join("", result.Where(e => !String.IsNullOrEmpty(e)));
int DayDateInt = 0;
int.TryParse(finalresult, out DayDateInt);
I have used this one-liner to pull all numbers from any string.
var phoneNumber = "(555)123-4567";
var numsOnly = string.Join("", new Regex("[0-9]").Matches(phoneNumber)); // 5551234567
string verificationCode ="dmdsnjds5344gfgk65585";
string code = "";
Regex r1 = new Regex("\\d+");
Match m1 = r1.Match(verificationCode);
while (m1.Success)
{
code += m1.Value;
m1 = m1.NextMatch();
}
Did the reverse of one of the answers to this question:
How to remove numbers from string using Regex.Replace?
// Pull out only the numbers from the string using LINQ
var numbersFromString = new String(input.Where(x => x >= '0' && x <= '9').ToArray());
var numericVal = Int32.Parse(numbersFromString);
Here is my Algorithm
//Fast, C Language friendly
public static int GetNumber(string Text)
{
int val = 0;
for(int i = 0; i < Text.Length; i++)
{
char c = Text[i];
if (c >= '0' && c <= '9')
{
val *= 10;
//(ASCII code reference)
val += c - 48;
}
}
return val;
}
static string GetdigitFromString(string str)
{
char[] refArray = { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9' };
char[] inputArray = str.ToCharArray();
string ext = string.Empty;
foreach (char item in inputArray)
{
if (refArray.Contains(item))
{
ext += item.ToString();
}
}
return ext;
}
here is my solution
string var = "Hello345wor705Ld";
string alpha = string.Empty;
string numer = string.Empty;
foreach (char str in var)
{
if (char.IsDigit(str))
numer += str.ToString();
else
alpha += str.ToString();
}
Console.WriteLine("String is: " + alpha);
Console.WriteLine("Numeric character is: " + numer);
Console.Read();
You will have to use Regex as \d+
\d matches digits in the given string.
string s = "kg g L000145.50\r\n";
char theCharacter = '.';
var getNumbers = (from t in s
where char.IsDigit(t) || t.Equals(theCharacter)
select t).ToArray();
var _str = string.Empty;
foreach (var item in getNumbers)
{
_str += item.ToString();
}
double _dou = Convert.ToDouble(_str);
MessageBox.Show(_dou.ToString("#,##0.00"));
Using #tim-pietzcker answer from above, the following will work for PowerShell.
PS C:\> $str = '1 test'
PS C:\> [regex]::match($str,'\d+').value
1
I want to remove all underscores from a string with the uppercase of the character following the underscore. So for example: _my_string_ becomes: MyString similarly: my_string becomes MyString
Is there a simpler way to do it? I currently have the following (assuming no input has two consecutive underscores):
StringBuilder sb = new StringBuilder();
int i;
for (i = 0; i < input.Length - 1; i++)
{
if (input[i] == '_')
sb.Append(char.ToUpper(input[++i]));
else if (i == 0)
sb.Append(char.ToUpper(input[i]));
else
sb.Append(input[i]);
}
if (i < input.Length && input[i] != '_')
sb.Append(input[i]);
return sb.ToString();
Now I know this is not totally related, but I thought to run some numbers on the implementations provided in the answers, and here are the results in Milliseconds for each implementation using 1000000 iterations of the string: "_my_string_121_a_" :
Achilles: 313
Raj: 870
Damian: 7916
Dmitry: 5380
Equalsk: 574
method utilised:
Stopwatch stp = new Stopwatch();
stp.Start();
for (int i = 0; i < 1000000; i++)
{
sb = Test("_my_string_121_a_");
}
stp.Stop();
long timeConsumed= stp.ElapsedMilliseconds;
In the end I think I'll go with Raj's implementation, because it's just very simple and easy to understand.
This must do it using ToTitleCase using System.Globalization namespace
static string toCamel(string input)
{
TextInfo info = CultureInfo.CurrentCulture.TextInfo;
input= info.ToTitleCase(input).Replace("_", string.Empty);
return input;
}
Shorter (regular expressions), but I doubt if it's better (regular expressions are less readable):
string source = "_my_string_123__A_";
// MyString123A
string result = Regex
// _ + lower case Letter -> upper case letter (thanks to Wiktor Stribiżew)
.Replace(source, #"(_+|^)(\p{Ll})?", match => match.Groups[2].Value.ToUpper())
// all the other _ should be just removed
.Replace("_", "");
Loops over each character and converts to uppercase as necessary.
public string GetNewString(string input)
{
var convert = false;
var sb = new StringBuilder();
foreach (var c in input)
{
if (c == '_')
{
convert = true;
continue;
}
if (convert)
{
sb.Append(char.ToUpper(c));
convert = false;
continue;
}
sb.Append(c);
}
return sb.ToString().First().ToString().ToUpper() + sb.ToString().Substring(1);
}
Usage:
GetNewString("my_string");
GetNewString("___this_is_anewstring_");
GetNewString("___this_is_123new34tring_");
Output:
MyString
ThisIsAnewstring
ThisIs123new34tring
Try with Regex:
var regex = new Regex("^[a-z]|_[a-z]?");
var result = regex.Replace("my_string_1234", x => x.Value== "_" ? "" : x.Value.Last().ToString().ToUpper());
Tested with:
my_string -> MyString
_my_string -> MyString
_my_string_ -> MyString
You need convert snake case to camel case, You can use this code it's working for me
var x ="_my_string_".Split(new[] {"_"}, StringSplitOptions.RemoveEmptyEntries)
.Select(s => char.ToUpperInvariant(s[0]) + s.Substring(1, s.Length - 1))
.Aggregate(string.Empty, (s1, s2) => s1 + s2);
x = MyString
static string toCamel(string input)
{
StringBuilder sb = new StringBuilder();
int i;
for (i = 0; i < input.Length; i++)
{
if ((i == 0) || (i > 0 && input[i - 1] == '_'))
sb.Append(char.ToUpper(input[i]));
else
sb.Append(char.ToLower(input[i]));
}
return sb.ToString();
}
I want to concatenate two strings in such a way, that after the first character of the first string, the first character of second string comes, and then the second character of first string comes and then the second character of the second string comes and so on. Best explained by some example cases:
s1="Mark";
s2="Zukerberg"; //Output=> MZaurkkerberg
if:
s1="Zukerberg";
s2="Mark" //Output=> ZMuakrekrberg
if:
s1="Zukerberg";
s2="Zukerberg"; //Output=> ZZuukkeerrbbeerrgg
I've written the following code which gives the expected output but its seems to be a lot of code. Is there any more efficient way for doing this?
public void SpecialConcat(string s1, string s2)
{
string[] concatArray = new string[s1.Length + s2.Length];
int k = 0;
string final = string.Empty;
string superFinal = string.Empty;
for (int i = 0; i < s1.Length; i++)
{
for (int j = 0; j < s2.Length; j++)
{
if (i == j)
{
concatArray[k] = s1[i].ToString() + s2[j].ToString();
final = string.Join("", concatArray);
}
}
k++;
}
if (s1.Length > s2.Length)
{
string subOne = s1.Remove(0, s2.Length);
superFinal = final + subOne;
}
else if (s2.Length > s1.Length)
{
string subTwo = s2.Remove(0, s1.Length);
superFinal = final + subTwo;
}
else
{
superFinal = final;
}
Response.Write(superFinal);
}
}
I have written the same logic in Javascript also, which works fine but again a lot of code.
var s1 = "Mark";
var s2 = "Zukerberg";
var common = string.Concat(s1.Zip(s2, (a, b) => new[]{a, b}).SelectMany(c => c));
var shortestLength = Math.Min(s1.Length, s2.Length);
var result =
common + s1.Substring(shortestLength) + s2.Substring(shortestLength);
var stringBuilder = new StringBuilder();
for (int i = 0; i < Math.Max(s1.Length, s2.Length); i++)
{
if (i < s1.Length)
stringBuilder.Append(s1[i]);
if (i < s2.Length)
stringBuilder.Append(s2[i]);
}
string result = stringBuilder.ToString();
In JavaScript, when working with strings, you are also working with arrays, so it will be easier. Also + will concatenate for you. Replace string indexing with charAt if you want IE7- support.
Here is the fiddle:
http://jsfiddle.net/z6XLh/1
var s1 = "Mark";
var s2 = "ZuckerFace";
var out ='';
var l = s1.length > s2.length ? s1.length : s2.length
for(var i = 0; i < l; i++) {
if(s1[i]) {
out += s1[i];
}
if(s2[i]){
out += s2[i];
}
}
console.log(out);
static string Join(string a, string b)
{
string returnVal = "";
int length = Math.Min(a.Length, b.Length);
for (int i = 0; i < length; i++)
returnVal += "" + a[i] + b[i];
if (a.Length > length)
returnVal += a.Substring(length);
else if(b.Length > length)
returnVal += b.Substring(length);
return returnVal;
}
Could possibly be improved through stringbuilder
Just for the sake of curiosity, here's an unreadable one-liner (which I have nevertheless split over multiple lines ;))
This uses the fact that padding a string to a certain length does nothing if the string is already at least that length. That means padding each string to the length of the other string will have the result of padding out with spaces the shorter one to the length of the longer one.
Then we use .Zip() to concatenate each of the pairs of characters into a string.
Then we call string.Concat(IEnumerable<string>) to concatenate the zipped strings into a single string.
Finally, we remove the extra padding spaces we introduced earlier by using string.Replace().
var result = string.Concat
(
s1.PadRight(s2.Length)
.Zip
(
s2.PadRight(s1.Length),
(a,b)=>string.Concat(a,b)
)
).Replace(" ", null);
On one line [insert Coding Horror icon here]:
var result = string.Concat(s1.PadRight(s2.Length).Zip(s2.PadRight(s1.Length), (a,b)=>string.Concat(a,b))).Replace(" ", null);
Just off the top of my head, this is how I might do it.
var s1Length = s1.Length;
var s2Length = s2.Length;
var count = 0;
var o = "";
while (s1Length + s2Length > 0) {
if (s1Length > 0) {
s1Length--;
o += s1[count];
}
if (s2Length > 0) {
s2Length--;
o += s2[count];
}
count++;
}
Here's another one-liner:
var s1 = "Mark";
var s2 = "Zukerberg";
var result = string.Join("",
Enumerable.Range(0, s1.Length).ToDictionary(x => x * 2, x => s1[x])
.Concat(Enumerable.Range(0, s2.Length).ToDictionary(x => x * 2+1, x => s2[x]))
.OrderBy(d => d.Key).Select(d => d.Value));
Basically, this converts both strings into dictionaries with keys that will get the resulting string to order itself correctly. The Enumerable range is used to associate an index with each letter in the string. When we store the dictionaries, it multiplies the index on s1 by 2, resulting in <0,M>,<2,a>,<4,r>,<6,k>, and multiplies s2 by 2 then adds 1, resulting in <1,Z>,<3,u>,<5,k>, etc.
Once we have these dictionaries, we combine them with the .Concat and sort them with the .OrderBy,which gives us <0,M>,<1,Z>,<2,a>,<3,u>,... Then we just dump them into the final string with the string.join at the beginning.
Ok, this is the *second shortest solution I could come up with:
public string zip(string s1, string s2)
{
return (string.IsNullOrWhiteSpace(s1+s2))
? (s1[0] + "" + s2[0] + zip(s1.Substring(1) + " ", s2.Substring(1) + " ")).Replace(" ", null)
: "";
}
var result = zip("mark","zukerberg");
Whoops! My original shortest was the same as mark's above...so, second shortest i could come up with! I had hoped I could really trim it down with the recursion, but not so much.
var sWordOne = "mark";// ABCDEF
var sWordTwo = "zukerberg";// 123
var result = (sWordOne.Length > sWordTwo.Length) ? zip(sWordOne, sWordTwo) : zip(sWordTwo, sWordOne);
//result = "zmuakrekrberg"
static string zip(string sBiggerWord, string sSmallerWord)
{
if (sBiggerWord.Length < sSmallerWord.Length) return string.Empty;// Invalid
if (sSmallerWord.Length == 0) sSmallerWord = " ";
return string.IsNullOrEmpty(sBiggerWord) ? string.Empty : (sBiggerWord[0] + "" + sSmallerWord[0] + zip(sBiggerWord.Substring(1),sSmallerWord.Substring(1))).Replace(" ","");
}
A simple alternative without Linq witchcraft:
string Merge(string one, string two)
{
var buffer = new char[one.Length + two.Length];
var length = Math.Max(one.Length, two.Length);
var index = 0;
for (var i = 0; i < length; i ++)
{
if (i < one.Length) buffer[index++] = one[i];
if (i < two.Length) buffer[index++] = two[i];
}
return new string(buffer);
}
Not entirely sure this is possible, but say I have two strings like so:
"IAmAString-00001"
"IAmAString-00023"
What would be a quick'n'easy way to iterate from IAmAString-0001 to IAmAString-00023 by moving up the index of just the numbers on the end?
The problem is a bit more general than that, for example the string I could be dealing could be of any format but the last bunch of chars will always be numbers, so something like Super_Confusing-String#w00t0003 and in that case the last 0003 would be what I'd use to iterate through.
Any ideas?
You can use char.IsDigit:
static void Main(string[] args)
{
var s = "IAmAString-00001";
int index = -1;
for (int i = 0; i < s.Length; i++)
{
if (char.IsDigit(s[i]))
{
index = i;
break;
}
}
if (index == -1)
Console.WriteLine("digits not found");
else
Console.WriteLine("digits: {0}", s.Substring(index));
}
which produces this output:
digits: 00001
string.Format and a for loop should do what you want.
for(int i = 0; i <=23; i++)
{
string.Format("IAmAString-{0:D4}",i);
}
or something close to that (not sitting in front of a compiler).
string start = "IAmAString-00001";
string end = "IAmAString-00023";
// match constant part and ending digits
var matchstart = Regex.Match(start,#"^(.*?)(\d+)$");
int numberstart = int.Parse(matchstart.Groups[2].Value);
var matchend = Regex.Match(end,#"^(.*?)(\d+)$");
int numberend = int.Parse(matchend.Groups[2].Value);
// constant parts must be the same
if (matchstart.Groups[1].Value != matchend.Groups[1].Value)
throw new ArgumentException("");
// create a format string with same number of digits as original
string format = new string('0', matchstart.Groups[2].Length);
for (int ii = numberstart; ii <= numberend; ++ii)
Console.WriteLine(matchstart.Groups[1].Value + ii.ToString(format));
You could use a Regex:
var match=Regex.Match("Super_Confusing-String#w00t0003",#"(?<=(^.*\D)|^)\d+$");
if(match.Success)
{
var val=int.Parse(match.Value);
Console.WriteLine(val);
}
To answer more specifically, you could use named groups to extract what you need:
var match=Regex.Match(
"Super_Confusing-String#w00t0003",
#"(?<prefix>(^.*\D)|^)(?<digits>\d+)$");
if(match.Success)
{
var prefix=match.Groups["prefix"].Value;
Console.WriteLine(prefix);
var val=int.Parse(match.Groups["digits"].Value);
Console.WriteLine(val);
}
If you can assume that the last 5 characters are the number then:
string prefix = "myprefix-";
for (int i=1; i <=23; i++)
{
Console.WriteLine(myPrefix+i.ToString("D5"));
}
This function will find the trailing number.
private int FindTrailingNumber(string str)
{
string numString = "";
int numTest;
for (int i = str.Length - 1; i > 0; i--)
{
char c = str[i];
if (int.TryParse(c.ToString(), out numTest))
{
numString = c + numString;
}
}
return int.Parse(numString);
}
Assuming all your base strings are the same, this would iterate between strings.
string s1 = "asdf123";
string s2 = "asdf127";
int num1 = FindTrailingNumber(s1);
int num2 = FindTrailingNumber(s2);
string strBase = s1.Replace(num1.ToString(), "");
for (int i = num1; i <= num2; i++)
{
Console.WriteLine(strBase + i.ToString());
}
I think it would be better if you do the search from the last (Rick already upvoted you since it was ur logic :-))
static void Main(string[] args)
{
var s = "IAmAString-00001";
int index = -1;
for (int i = s.Length - 1; i >=0; i--)
{
if (!char.IsDigit(s[i]))
{
index = i;
break;
}
}
if (index == -1)
Console.WriteLine("digits not found");
else
Console.WriteLine("digits: {0}", s.Substring(index));
Console.ReadKey();
}
HTH
If the last X numbers are always digits, then:
int x = 5;
string s = "IAmAString-00001";
int num = int.Parse(s.Substring(s.Length - x, x));
Console.WriteLine("Your Number is: {0}", num);
If the last digits can be 3, 4, or 5 in length, then you will need a little more logic:
int x = 0;
string s = "IAmAString-00001";
foreach (char c in s.Reverse())//Use Reverse() so you start with digits only.
{
if(char.IsDigit(c) == false)
break;//If we start hitting non-digit characters, then exit the loop.
++x;
}
int num = int.Parse(s.Substring(s.Length - x, x));
Console.WriteLine("Your Number is: {0}", num);
I'm not good with complicated RegEx. Because of this, I always shy away from it when maximum optimization is unnecessary. The reason for this is RegEx doesn't always parse strings the way you expect it to. If there is and alternate solution that will still run fast then I'd rather go that route as it's easier for me to understand and know that it will work with any combination of strings.
For Example: if you use some of the other solutions presented here with a string like "I2AmAString-000001", then you will get "2000001" as your number instead of "1".
I need to parse a decimal integer that appears at the start of a string.
There may be trailing garbage following the decimal number. This needs to be ignored (even if it contains other numbers.)
e.g.
"1" => 1
" 42 " => 42
" 3 -.X.-" => 3
" 2 3 4 5" => 2
Is there a built-in method in the .NET framework to do this?
int.TryParse() is not suitable. It allows trailing spaces but not other trailing characters.
It would be quite easy to implement this but I would prefer to use the standard method if it exists.
You can use Linq to do this, no Regular Expressions needed:
public static int GetLeadingInt(string input)
{
return Int32.Parse(new string(input.Trim().TakeWhile(c => char.IsDigit(c) || c == '.').ToArray()));
}
This works for all your provided examples:
string[] tests = new string[] {
"1",
" 42 ",
" 3 -.X.-",
" 2 3 4 5"
};
foreach (string test in tests)
{
Console.WriteLine("Result: " + GetLeadingInt(test));
}
foreach (var m in Regex.Matches(" 3 - .x. 4", #"\d+"))
{
Console.WriteLine(m);
}
Updated per comments
Not sure why you don't like regular expressions, so I'll just post what I think is the shortest solution.
To get first int:
Match match = Regex.Match(" 3 - .x. - 4", #"\d+");
if (match.Success)
Console.WriteLine(int.Parse(match.Value));
There's no standard .NET method for doing this - although I wouldn't be surprised to find that VB had something in the Microsoft.VisualBasic assembly (which is shipped with .NET, so it's not an issue to use it even from C#).
Will the result always be non-negative (which would make things easier)?
To be honest, regular expressions are the easiest option here, but...
public static string RemoveCruftFromNumber(string text)
{
int end = 0;
// First move past leading spaces
while (end < text.Length && text[end] == ' ')
{
end++;
}
// Now move past digits
while (end < text.Length && char.IsDigit(text[end]))
{
end++;
}
return text.Substring(0, end);
}
Then you just need to call int.TryParse on the result of RemoveCruftFromNumber (don't forget that the integer may be too big to store in an int).
I like #Donut's approach.
I'd like to add though, that char.IsDigit and char.IsNumber also allow for some unicode characters which are digits in other languages and scripts (see here).
If you only want to check for the digits 0 to 9 you could use "0123456789".Contains(c).
Three example implementions:
To remove trailing non-digit characters:
var digits = new string(input.Trim().TakeWhile(c =>
("0123456789").Contains(c)
).ToArray());
To remove leading non-digit characters:
var digits = new string(input.Trim().SkipWhile(c =>
!("0123456789").Contains(c)
).ToArray());
To remove all non-digit characters:
var digits = new string(input.Trim().Where(c =>
("0123456789").Contains(c)
).ToArray());
And of course: int.Parse(digits) or int.TryParse(digits, out output)
This doesn't really answer your question (about a built-in C# method), but you could try chopping off characters at the end of the input string one by one until int.TryParse() accepts it as a valid number:
for (int p = input.Length; p > 0; p--)
{
int num;
if (int.TryParse(input.Substring(0, p), out num))
return num;
}
throw new Exception("Malformed integer: " + input);
Of course, this will be slow if input is very long.
ADDENDUM (March 2016)
This could be made faster by chopping off all non-digit/non-space characters on the right before attempting each parse:
for (int p = input.Length; p > 0; p--)
{
char ch;
do
{
ch = input[--p];
} while ((ch < '0' || ch > '9') && ch != ' ' && p > 0);
p++;
int num;
if (int.TryParse(input.Substring(0, p), out num))
return num;
}
throw new Exception("Malformed integer: " + input);
string s = " 3 -.X.-".Trim();
string collectedNumber = string.empty;
int i;
for (x = 0; x < s.length; x++)
{
if (int.TryParse(s[x], out i))
collectedNumber += s[x];
else
break; // not a number - that's it - get out.
}
if (int.TryParse(collectedNumber, out i))
Console.WriteLine(i);
else
Console.WriteLine("no number found");
This is how I would have done it in Java:
int parseLeadingInt(String input)
{
NumberFormat fmt = NumberFormat.getIntegerInstance();
fmt.setGroupingUsed(false);
return fmt.parse(input, new ParsePosition(0)).intValue();
}
I was hoping something similar would be possible in .NET.
This is the regex-based solution I am currently using:
int? parseLeadingInt(string input)
{
int result = 0;
Match match = Regex.Match(input, "^[ \t]*\\d+");
if (match.Success && int.TryParse(match.Value, out result))
{
return result;
}
return null;
}
Might as well add mine too.
string temp = " 3 .x£";
string numbersOnly = String.Empty;
int tempInt;
for (int i = 0; i < temp.Length; i++)
{
if (Int32.TryParse(Convert.ToString(temp[i]), out tempInt))
{
numbersOnly += temp[i];
}
}
Int32.TryParse(numbersOnly, out tempInt);
MessageBox.Show(tempInt.ToString());
The message box is just for testing purposes, just delete it once you verify the method is working.
I'm not sure why you would avoid Regex in this situation.
Here's a little hackery that you can adjust to your needs.
" 3 -.X.-".ToCharArray().FindInteger().ToList().ForEach(Console.WriteLine);
public static class CharArrayExtensions
{
public static IEnumerable<char> FindInteger(this IEnumerable<char> array)
{
foreach (var c in array)
{
if(char.IsNumber(c))
yield return c;
}
}
}
EDIT:
That's true about the incorrect result (and the maintenance dev :) ).
Here's a revision:
public static int FindFirstInteger(this IEnumerable<char> array)
{
bool foundInteger = false;
var ints = new List<char>();
foreach (var c in array)
{
if(char.IsNumber(c))
{
foundInteger = true;
ints.Add(c);
}
else
{
if(foundInteger)
{
break;
}
}
}
string s = string.Empty;
ints.ForEach(i => s += i.ToString());
return int.Parse(s);
}
private string GetInt(string s)
{
int i = 0;
s = s.Trim();
while (i<s.Length && char.IsDigit(s[i])) i++;
return s.Substring(0, i);
}
Similar to Donut's above but with a TryParse:
private static bool TryGetLeadingInt(string input, out int output)
{
var trimmedString = new string(input.Trim().TakeWhile(c => char.IsDigit(c) || c == '.').ToArray());
var canParse = int.TryParse( trimmedString, out output);
return canParse;
}