Topic: Increment a Number in a String

[SteveK]

Hi,

I have a string. I need a function that finds the last number in the string and increments it by an integer (parameter) then returns the string again.
I'm sure you can do this with regular expressions but I don't know how.

Example 1: (negative increment)
input string = a3
value to increment = -1
string returned = a2

Example 2: (multiple numbers in the string)
input string = ab12cd34e
value to increment = 2
string returned = ab12cd36e

Example 3: (ignoring decimal places)
input string a1.9b
value to increment = 1
string returned = a1.10b

Programming in C#. Any help is appreciated.

[pkohut]

Example 2: (multiple numbers in the string)
input string = ab12cd34e
value to increment = 2
string returned = ab12cd36e

Example 3: (ignoring decimal places)
input string a1.9b
value to increment = 1
string returned = a1.10b

Are the numbers limited to a range and subject to rollover, like an odometer? Can't tell from examples 1 and 2. Example 3 suggests not. Let's clarify using a modified example 2.

Code: [Select]

input string ab12cd98e
value to increment = 2
string returned = ab12cd00e or ab12cd100e ??

Similar question for negative increments. And with negative increments, is 0 a floor or are negative results acceptable?

[Andrey Bushman]

Code: [Select]

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace ConsoleTest
{
    class Program
    {
        static void Main(string[] args)
        {
            Console.WriteLine(Incr("asdf123", 5));
            Console.WriteLine(Incr("asdf555_red123", -7));
            Console.Read();
        }

        static string Incr(string text, int increment)
        {
            int i = Int32.Parse(new string(text.Reverse().TakeWhile(n => Char.IsNumber(n)).Reverse().ToArray()));
            string name = text.Substring(0, text.Length - i.ToString().Length);
            return name + (i + increment);
        }
    }
}


[SteveK]

Are the numbers limited to a range and subject to rollover, like an odometer? Can't tell from examples 1 and 2. Example 3 suggests not. Let's clarify using a modified example 2.

Code: [Select]

input string ab12cd98e
value to increment = 2
string returned = ab12cd00e or ab12cd100e ??

Similar question for negative increments. And with negative increments, is 0 a floor or are negative results acceptable?

pkohut, I should have added, range is not limited in positive direction, and assume 0 is floor.

Andrey, I will try your code and let you know.

[SteveK]

Code: [Select]

        static string Incr(string text, int increment)
        {
            int i = Int32.Parse(new string(text.Reverse().TakeWhile(n => Char.IsNumber(n)).Reverse().ToArray()));
            string name = text.Substring(0, text.Length - i.ToString().Length);
            return name + (i + increment);
        }


Thanks for the code Andrey. It takes me further along than I was, however I get an error when letters are at the end of my string. The last number can be anywhere in the string, even at the start.

[fixo]

Hi,

I have a string. I need a function that finds the last number in the string and increments it by an integer (parameter) then returns the string again.
I'm sure you can do this with regular expressions but I don't know how.

Example 1: (negative increment)
input string = a3
value to increment = -1
string returned = a2

Example 2: (multiple numbers in the string)
input string = ab12cd34e
value to increment = 2
string returned = ab12cd36e

Example 3: (ignoring decimal places)
input string a1.9b
value to increment = 1
string returned = a1.10b

Programming in C#. Any help is appreciated.

Hi Steve
Send me test message on my home address
coz I've lost your e-mail
I have complete project (not finished yet,
but it may helps)
I've used RegularExpression to rebuild sttring

~'J'~

[SteveK]

Hi Oleg,

You have a complete project? But I'm just after one function! 

steve

[Andrey Bushman]

The last number can be anywhere in the string, even at the start.

Code: [Select]

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace ConsoleTest
{
    class Program
    {
        static void Main(string[] args)
        {
            Console.WriteLine(Incr("asdf123", 5));
            Console.WriteLine(Incr("asdf555_red123", -7));
            Console.WriteLine(Incr("asdf555_red123dwq", -2));
            Console.WriteLine(Incr("543asdf", -7));
            Console.WriteLine(Incr("asdf555_red123dwq1", -5));
            Console.WriteLine(Incr("rrasdf", 8));
            Console.Read();
        }

        static string Incr(string text, int increment)
        {
            if (text.Where(n => Char.IsNumber(n)).Count() == 0)
            {
                Console.WriteLine("string '{0}' not contain of number", text);
                return string.Empty;
            }
            string revText = new string(text.Reverse().ToArray());
            string a = new string(revText.TakeWhile(n => !Char.IsNumber(n)).ToArray());
            int b = Int32.Parse(new string(revText.Skip(a.Length).TakeWhile(n => Char.IsNumber(n)).Reverse().ToArray())) + increment;
            string c = revText.Substring(a.Length + b.ToString().Length);
            StringBuilder sb = new StringBuilder();
            sb.Append(a);
            sb.Append(new string(b.ToString().Reverse().ToArray()));
            sb.Append(c);            
            return new string(sb.ToString().Reverse().ToArray());
        }
    }
}


[SteveK]

Thank you Hwd, I can deffinately use this.

Cheers!

[Andrey Bushman]

Thank you Hwd, I can deffinately use this.

Cheers!

I will forgive pardons - I have skipped an error for it variant string:
"asdf555_red123dwq00001":

I has rectified an error:

Code: [Select]

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace ConsoleTest
{
    class Program
    {
        static void Main(string[] args)
        {
            Console.WriteLine(Incr("asdf123", 5));
            Console.WriteLine(Incr("asdf555_red123", -7));
            Console.WriteLine(Incr("asdf555_red123dwq", -2));
            Console.WriteLine(Incr("543asdf", -7));
            Console.WriteLine(Incr("asdf555_red123dwq1", -5));
            Console.WriteLine(Incr("asdf555_red123dwq00001", -5));//It test add
            Console.WriteLine(Incr("rrasdf", 8));
            Console.Read();
        }

        static string Incr(string text, int increment)
        {
            if (text.Where(n => Char.IsNumber(n)).Count() == 0)
            {
                Console.WriteLine("string '{0}' not contants of nomber", text);
                return string.Empty;
            }
            string revText = new string(text.Reverse().ToArray());
            string a = new string(revText.TakeWhile(n => !Char.IsNumber(n)).ToArray());
            string z = new string(revText.Skip(a.Length).TakeWhile(n => Char.IsNumber(n)).Reverse().ToArray());
            int b = Int32.Parse(z) + increment;
            if (b > 0)
            {
                z = z.Length == b.ToString().Length ? b.ToString() : new string('0', z.Length - b.ToString().Length) + b;
            }
            else
            {
                z = z.Length == b.ToString().Length ? b.ToString() : new string('0', z.Length + 1 - b.ToString().Replace("-","").Length) + Math.Abs(b);
            }
           
            string c = revText.Substring(a.Length + z.Length);
            StringBuilder sb = new StringBuilder();
            sb.Append(a);
            sb.Append(new string(z.Reverse().ToArray()));
            sb.Append(c);           
            return new string(sb.ToString().Reverse().ToArray());
        }
    }
}


[SteveK]

Thanks for your help so far Hwd.

I did find another error though. Try for example:

Code: [Select]

Console.WriteLine(Incr("9a", 1));
Console.WriteLine(Incr("a99b", 1));

Edit: Also, a problem with having Replace("-","") in the code is that sometimes there are hyphen's in the string and it'd remove them.

[Andrey Bushman]

Thanks for your help so far Hwd.

I did find another error though. Try for example:

Code: [Select]

Console.WriteLine(Incr("9a", 1));
Console.WriteLine(Incr("a99b", 1));

Edit: Also, a problem with having Replace("-","") in the code is that sometimes there are hyphen's in the string and it'd remove them.

Test it please:

Code: [Select]

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace ConsoleTest
{
    class Program
    {
        static void Main(string[] args)
        {
            Console.WriteLine(Incr("asdf123", 5));
            Console.WriteLine(Incr("asdf555_red123", -7));
            Console.WriteLine(Incr("asdf555_red123dwq", -2));
            Console.WriteLine(Incr("543asdf", -7));
            Console.WriteLine(Incr("asdf555_red123dwq1", -5));
            Console.WriteLine(Incr("asdf555_red123dwq00001", -5));
            Console.WriteLine(Incr("9a", 1));
            Console.WriteLine(Incr("a99b", 1));
            Console.WriteLine(Incr("999", -11));
            Console.WriteLine(Incr("rrasdf", 8));
           
            Console.Read();
        }

        static string Incr(string text, int increment)
        {
            if (text.Where(n => Char.IsNumber(n)).Count() == 0)
            {
                Console.WriteLine("string '{0}' not contants of nomber", text);
                return string.Empty;
            }
            string revText = new string(text.Reverse().ToArray());
            string a = new string(revText.TakeWhile(n => !Char.IsNumber(n)).ToArray());
            string z = new string(revText.Skip(a.Length).TakeWhile(n => Char.IsNumber(n)).Reverse().ToArray());
            string d = z;
            int zc = z.Length - Int32.Parse(z).ToString().Length;// count of 0.
            int b = Int32.Parse(z) + increment;
            if (b > 0)
            {
                z = z.Length == b.ToString().Length ? b.ToString() : new string('0', zc) + b;
            }
            else
            {
                z = z.Length == b.ToString().Length ? b.ToString() : new string('0', zc + 1) + Math.Abs(b);
            }
           
            string c = revText.Substring(a.Length + d.Length);
            StringBuilder sb = new StringBuilder();
            sb.Append(a);
            sb.Append(new string(z.Reverse().ToArray()));
            sb.Append(c);           
            return new string(sb.ToString().Reverse().ToArray());
        }
    }
}


[SteveK]

That's better, no errors, thanks:

I was also messing around with it as I've learnt from your code and I came up with:

Code: [Select]

static string Incr(string text, int increment)
{
    if (text.Where(n => Char.IsNumber(n)).Count() == 0)
        return null;
    string revText = new string(text.Reverse().ToArray());
    string a = new string(revText.TakeWhile(n => !Char.IsNumber(n)).ToArray());
    string z = new string(revText.Skip(a.Length).TakeWhile(n => Char.IsNumber(n)).Reverse().ToArray());
    string y = new string(z.TakeWhile(n => n.Equals('0')).ToArray());
    string c = revText.Substring(a.Length + z.Length);
    int b = Int32.Parse(z) + increment;
    if (b < 0) b = 0;
    z = b.ToString();
    StringBuilder sb = new StringBuilder();
    sb.Append(a);
    sb.Append(new string(z.Reverse().ToArray()));
    sb.Append(y);
    sb.Append(c);
    return new string(sb.ToString().Reverse().ToArray());
}Very similar to yours. Again, thanks for your help Hwd. 

[Andrey Bushman]

Again, thanks for your help Hwd. 

[fixo]

That's better, no errors, thanks:

I was also messing around with it as I've learnt from your code and I came up with:

Code: [Select]

static string Incr(string text, int increment)
{
    if (text.Where(n => Char.IsNumber(n)).Count() == 0)
        return null;
    string revText = new string(text.Reverse().ToArray());
    string a = new string(revText.TakeWhile(n => !Char.IsNumber(n)).ToArray());
    string z = new string(revText.Skip(a.Length).TakeWhile(n => Char.IsNumber(n)).Reverse().ToArray());
    string y = new string(z.TakeWhile(n => n.Equals('0')).ToArray());
    string c = revText.Substring(a.Length + z.Length);
    int b = Int32.Parse(z) + increment;
    if (b < 0) b = 0;
    z = b.ToString();
    StringBuilder sb = new StringBuilder();
    sb.Append(a);
    sb.Append(new string(z.Reverse().ToArray()));
    sb.Append(y);
    sb.Append(c);
    return new string(sb.ToString().Reverse().ToArray());
}Very similar to yours. Again, thanks for your help Hwd. 

Hope you don't mind but how about:

Code: [Select]

Console.WriteLine(Incr("asdf0004", -5));
~'J'~