How to search list array with in the range

Question

3.00/5 (1 vote)

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Hi friends,

I need to search an array which has 600 items.My requirement is i need to search the array say from index 200 to 400. How can i achieve this?

What I have tried:

C#

var lines = File.ReadAllLines(csvpath).Select(x => x.Split(',')).ToList();
        
var portdetails = lines.Where(acc => acc[0].Trim() == "PORTDTLS").ToList();

C#

Posted 2-Oct-16 23:57pm

jinesh sam

Updated 3-Oct-16 6:25am

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3 solutions

Solution 2

Copy the required elements to another list (see List(T).CopyTo Method (Int32, T[], Int32, Int32) (System.Collections.Generic)[^]).

Posted 3-Oct-16 0:11am

Richard MacCutchan

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Karthik_Mahalingam · Accepted Answer · 2016-10-03T06:25:00

Solution 3

try this

C#

var itemsFrom200to400 = lines.Skip(200).Take(200).ToList();
var portdetails = itemsFrom200to400.Where(acc => acc[0].Trim() == "PORTDTLS").ToList();

Posted 3-Oct-16 6:25am

Karthik_Mahalingam

Comments

Philippe Mori 4-Oct-16 9:56am

Good solution but the first ToList() call is superfluous. Useless memory allocation and waste of time.

#realJSOP · Accepted Answer · 2016-10-03T00:11:00

Solution 1

I don't think that's going to result in what you're actually after.

Try this:

C#

var portdetails = lines.Where(acc => lines.IndexOf(acc) >= 200 && lines.IndexOf(acc) <= 400 && acc.Trim().StartsWith("PORTDTLS ").ToList();

After you get the lines, THEN split them on the comma separator.

Another point - is the index range ALWAYS going to be 200-400? How do you know this? How can you guarantee it. I think you need to step back and look at the problem again.

Posted 3-Oct-16 0:11am

#realJSOP

Comments

jinesh sam 4-Oct-16 4:58am

Thanks John:) For finding index i have separate method

Philippe Mori 4-Oct-16 10:02am

I think this solution would be inefficient as it could be... like O(n²) instead of O(n) as I don't believe that Linq to object would optimize such use of IndexOf. Also, if there be duplicate in the list, you might not get expected result as it would probably take the index of the first occurrence of the string instead of the actual one. Thus in OP example, if the same string existing at index 100 and 300, you would probably get neither...

#realJSOP 4-Oct-16 10:12am

I was merely giving him the answer he was looking for. I'm not concerned with "efficiency" because it's not *my* code. The call to ToList() isn't even necessary, but that's what he was doing, so that's what I did. As for using linq, linq is known to be slower , especially is you start stacking subsequent linq calls on each other. So, you can see that I'm perfectly aware of the "efficiencies", but chose to ignore them.

TECHNICALLY, my answer is appropriate, and does not warrant your 2-vote. BTW, I didn't notice an answer from you for this question - just criticism of the answers that were already here.

Finally, I know exactly what data he is working with because I answered an earlier question of his regarding the same data set.

Philippe Mori 4-Oct-16 10:28am

Well, I haven't provided a solution 3 + my comment would be my answer...

Although one does not always need to be concerned about efficiency, I do believe in writing code that is reasonably efficient. Thus in a case like that, I really thing that using Skip and Take as it solution 3 worth 2 extra votes.