Re: Sorting an Array - C# Discussion Boards

8-Dec-07 1:37

I have an Array arraylist

arraylist.Sort(); sorts the array on character 0-end of each element of the array.

How do I make it sort on the 60th charaacter to the end of each element of the array.

Anthony Mushrow8-Dec-07 2:07

Anthony Mushrow

8-Dec-07 2:07

You could do a bubble sort yourself, its only a few lines of code. You could even make your own little function out of it.

My current favourite word is: Bauble!

-SK Genius

electriac8-Dec-07 2:17

Re: Sorting an Array [modified]

8-Dec-07 2:17

Could you show me an example of the few lines of code.

TNX

Anthony Mushrow8-Dec-07 2:25

Anthony Mushrow

8-Dec-07 2:25

Just a simple bubble sort. Say you had an array of numbers ranging from 1 - 10 in any order:

do {
 bool Continue;
 for(int i=0; i<array.length-1; i++) {
  if(array[i] > array[i+1]) {
    int temp = array[i];
    array[i] = array[i+1];
    array[i+1] = temp;
    Continue = true;
  }
 }
}while(Continue);

Of course to start at 60 and go to the end, you would just start int i at 60, rather than 0. If you have something like a string in your array, the string class has methods that compare two strings, so you'd need to check those out.

EDIT:Fixed the code, stupid < Roll eyes | :rolleyes:

My current favourite word is: Bauble!

-SK Genius

modified on Saturday, December 08, 2007 8:39:46 AM

electriac8-Dec-07 2:35

8-Dec-07 2:35

Yes it is a string. I have been able to solve the problem by writing the array to a text file unsorted.txt and then doing a DOS sort /+60 usorted.txt > sorted.txt and reading the file back into the array but thats really messy.

I will try to implement your suggestion

TNX

Ennis Ray Lynch, Jr.8-Dec-07 2:32

Ennis Ray Lynch, Jr.

8-Dec-07 2:32

Write a comparer for the object you are storing int the array. Several of the .NET list objects will take, as a parameter to sort, the comparer to use. In fact, even if you don't pass one the default comparer will likely use your version.

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Happiness in intelligent people is the rarest thing I know. -- Ernest Hemingway

electriac8-Dec-07 2:38

8-Dec-07 2:38

I have spent a whole day trying to write a comarer and make sence out of MSDN's convoluted instructions but have not been able to get something that compiles and works.

Ennis Ray Lynch, Jr.8-Dec-07 2:47

Ennis Ray Lynch, Jr.

8-Dec-07 2:47

public class Foo : Comparer<foo> {
private string mMyString = new string('c', 100);
public override int Compare(Foo one, Foo two) {
return one.mMyString.Substring(59).CompareTo(two.mMyString.Substring(59));
}
}

Use System.Collections.Generic.List<foo> as the list.

Also, you may have to vary the code in the Compare method as I did not bother to test it.

Need a C# Consultant? I'm available.

Happiness in intelligent people is the rarest thing I know. -- Ernest Hemingway

Re: Sorting an Array [modified]

Guffa8-Dec-07 3:55

Guffa

8-Dec-07 3:55

A comparer is pretty simple. It's just a class with a Compare method that works like any other Compare method (like string.Compare for example).

Try this:

class SubstringComparer : IComparer<string> {
   private int _offset, _len;
   public SubstringComparer(int offset, int len) { _offset = offset; _len = len; }
   public override int Compare(string x, string y) {
      return string.Compare(x, _offset, y, _offset, _len);
   }
}

Array.Sort(myArray, new SubstringComparer(59, int.MaxValue));

modified on Saturday, December 08, 2007 2:31:24 PM

electriac8-Dec-07 4:17

8-Dec-07 4:17

This is my code that will not compile.

<br />
<br />
<br />
 class SubstringComparer : IComparer<string> <br />
        {   <br />
            private int _offset, _len;   <br />
            public SubstringComparer(int offset, int len) <br />
            { <br />
                _offset = offset; _len = len; <br />
            }   <br />
            public override int Compare(string x, string y) <br />
  //---------------------------------------------------------<br />
  // I get no suitable method found to override Compare<br />
  //--------------------------------------------------------- <br />
            {      <br />
                return string.Compare(x, _offset, y, _offset, _len);   <br />
            }<br />
        }<br />
        <br />
        private void button13_Click(object sender, EventArgs e)<br />
        {<br />
            ArrayList arraylist = new ArrayList();<br />
            for (int i = 0; i < listBox1.Items.Count; i++)<br />
            {<br />
                string temp = listBox1.Items[i].ToString();<br />
                if (temp.Length>65)<br />
                {<br />
                        arraylist.Add(temp);<br />
                }<br />
            }<br />
            Array.Sort(arraylist, new SubstringComparer(59, int.MaxValue));<br />
            listBox1.Items.Clear();<br />
            for (int i = 0; i < arraylist.Count; i++)<br />
                listBox1.Items.Add(arraylist[i]);<br />
        }<br />
    }<br />

TNX for the help

modified on Saturday, December 08, 2007 10:45:32 AM

Luc Pattyn8-Dec-07 7:53

Luc Pattyn

8-Dec-07 7:53

Hi George,

there are basically two ways (old and new):

1.
if you want to sort an ArrayList in a special way, you need to create an object
that implements IComparer (without < string> ) and knows how to compare
two items. Its signature MUST be public int Compare(object obj1, object obj2)

There is no override, by writing ": Icomparer" you promise to implement the formentioned method.

And you need to cast the arguments to strings explicitly, as in:
string str1=(string)obj1

2.
Starting with .NET 2.0 you can also use generic collections.

The code Guffa showed you is fine if you keep the strings in a generic list, that is
a List< string>. In that case you inherit
from IComparer< string> and your Compare method takes string
arguments directly, but still there is no override involved.
The generics stuff basically makes all the castings redundant.

Regards,

Luc Pattyn [Forum Guidelines] [My Articles]

Sorry for any delays in replying, I currently don't get e-mail notifications.

electriac8-Dec-07 9:36

8-Dec-07 9:36

Is it possible that my problem is associated with the fact that I am using .NET 3.5 and Visual 2008.

Luc Pattyn8-Dec-07 10:11

Luc Pattyn

8-Dec-07 10:11

Hi George,

I don't know for sure about 3.5/2008 since I haven't used them yet.
but there are some problems in the code you posted, as I pointed out before.
For one you should drop the "override" then choose either an ArrayList (1. in
my earlier reply) or List< string> (2) and make your Compare accordingly.

Smile | :)

Luc Pattyn [Forum Guidelines] [My Articles]

Sorry for any delays in replying, I currently don't get e-mail notifications.

DaveyM699-Dec-07 23:26

DaveyM69

9-Dec-07 23:26

I haven't investigated to see if there are any new 'features' in this regard - but Generic Lists, IComparer and IComparable definately function as before and none of the 'normal' methods have changed in VS2008/.NET3.5

To be honest, so far I've had no problems coding exactly the same as I did with 2005 with all classes/interfaces etc.

electriac10-Dec-07 8:39

10-Dec-07 8:39

I have found also that all my old code could migrate without problem.

Guffa8-Dec-07 8:30

Guffa

8-Dec-07 8:30

Oh, you are not using an array at all, but an ArrayList. That's a big difference.

Then you need a comparer that handles objects:

class SubstringComparer : IComparer {
private int _offset, _len;
public SubstringComparer(int offset, int len) {
_offset = offset; _len = len;
}
public override int Compare(object x, object y) {
return string.Compare((string)x, _offset, (string)y, _offset, _len);
}
}

And use it like this:

arraylist.Sort(new SubstringComparer(59, int.MaxValue));

Experience is the sum of all the mistakes you have done.

electriac8-Dec-07 9:31

8-Dec-07 9:31

Still will not compile

class SubstringComparer : IComparer
{
    private int _offset, _len;
    public SubstringComparer(int offset, int len)
    {
        _offset = offset; _len = len;
    }
    public override int Compare(object x, object y)
        //-----------------------------------------------------------------------
        //        On Compare I still get no suitable method to overide
        //
        //-----------------------------------------------------------------------
    {
        return string.Compare((string)x, _offset, (string)y, _offset, _len);
    }
}

private void button13_Click(object sender, EventArgs e)
{
    ArrayList arraylist = new ArrayList();
    for (int i = 0; i < listBox1.Items.Count; i++)
    {
        string temp = listBox1.Items[i].ToString();
        if (temp.Length>65)
        {
                arraylist.Add(temp);
        }
    }

    arraylist.Sort(new SubstringComparer(59, int.MaxValue));

    listBox1.Items.Clear();
    for (int i = 0; i < arraylist.Count; i++)
        listBox1.Items.Add(arraylist[i]);
}

Guffa8-Dec-07 9:50

Guffa

8-Dec-07 9:50

Silly me... It's an interface, so you don't override the methods. Just remove the override keyword.

Experience is the sum of all the mistakes you have done.

modified on Monday, December 10, 2007 7:05:57 PM

electriac10-Dec-07 8:37