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How to loop through number list to create sequence

Posted on 2008-06-13
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Last Modified: 2008-06-13
I have a listbox which contains a long list of numbers like this:

1123
1124
1125
1130
1131
1144
1145
1146
1155
1177
1179
1180
1181

I want to loop through this and return the sequences i.e. once the loop has completed the output would be:
1123 - 1125
1130 - 1131
1144 - 1146
1155
1177
1179 -1181

does this make sense?
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Question by:sterankin
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4 Comments
 
LVL 6

Expert Comment

by:Bruce_1975
ID: 21777892
does this make sense? is a question, you have to answer.
What is your intention to do this?
What is the required output format (string? some kind of Range-Object?)

Regards,
Bruce
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Author Comment

by:sterankin
ID: 21778000
Loop through one listbox which contains (this is a very short example):
1123
1124
1125
1130
1131
1144
1145
1146
1155
1177
1179
1180
1181

and display the following in another listbox:
1123 - 1125
1130 - 1131
1144 - 1146
1155
1177
1179 -1181

ie it should show the sequential unbroken ranges..

I tried creating a loop which looks at the next number in the list and seeing if it is equal to the previous number+1, its pretty close but not 100% right:

string seq=listBox2.Items[0].ToString();
for(int i =0; i<=listBox2.Items.Count;i++)
{
     if(i<listBox2.Items.Count-1)
 {

 if((Convert.ToInt32(listBox2.Items[i].ToString())) + 1 == (Convert.ToInt32(listBox2.Items[i+1].ToString())))
{
               seq  += " - " + listBox2.Items[i+1].ToString() ;
                listBox1.Items.Add(seq);
                seq="";

}
else
 {    

     listBox1.Items.Add(listBox2.Items[i].ToString());

}
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LVL 6

Accepted Solution

by:
Bruce_1975 earned 125 total points
ID: 21778426
Try this function.

Regards,
Bruce
private string[] GetRanges(int[] RawData)
{
    List<string> reply = new List<string>();
    for (int i = 1; i < RawData.Length; i++)
    {
        int start = RawData[i - 1];
 
        while (RawData[i - 1] + 1== RawData[i])
        {
            if (++i == RawData.Length)
                break;
        }
 
        int stop = RawData[i - 1];
 
        if (start == stop)
            reply.Add(start.ToString());
        else
            reply.Add(string.Concat(start," - ", stop));
    }
 
    return reply.ToArray();
}

Open in new window

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Author Comment

by:sterankin
ID: 21778806
Thanks Bruce!!
I see that is Generics?  I'm using VS 2003 which does not use Generics, but I tried it in 2005 and it worked ok.  I am unfamiliar with generics and it took me a while to work out how to use it correctly.

This is how I used it on a button click:

// create an int array to add the number to from the listbox
int[] arr =  new int [listBox2.Items.Count];
//add the numbers to the list box
            for(int i=0;i<listBox2.Items.Count-1;i++)
            {
                arr[i]=Convert.ToInt32(listBox2.Items[i]);
            }
//create a string array to hold the returned items
            string[] str = new string[listBox2.Items.Count];
//call the method
            str= GetRanges(arr);
//loop thourgh the string array and add to the list box
            for (int x = 0; x < str.Length; x++)
            {
                listBox1.Items.Add (str[x]);
            }

Thanks for your help, always good to learn something new :)
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