Custom Sort a list

Hello Guys,

I want to sort a list in a custom manner as follows

Given List Order = 1,2,3,4,5

***** CORRECTION : Required List Order = 2,3,5,4,1

please let me know how this can be achieved.

thank you all in advance.

 

If the given list was [ 10,9,8,7,6 ], what would the result be? Would it be [ 6, 8, 10, 9, 7 ], or would it be [ 10, 8, 6, 7, 9 ]?

 

https://stackoverflow.com/questions/273313/randomize-a-listt

 

The OP has not explained it well but there is a pattern to their requirement - at least, it does not appear to be random. What I am unsure about is whether the final arrangement is based on the values of the input elements or on their original positions. Hence my request for a clarification.

 

If you want to use custom rules to sort a list, take a look at this thread. It explains several methods of doing so.

 

Oh, I've just now noticed that it's not random. It's consecutive odd numbers increasing and then even numbers decreasing. I'm guessing it only looks so pretty when working with a sequence of consecutive numbers starting with an odd number.

And of course I applaud your belief that OP will log in for a second time.

 

@Doug_B the output would be [ 10, 8, 6, 7, 9 ]

 

Sorry for the late reply guys

 

also if the given order is : 1,2,3,4,5,6,7,8
Required List Order = 2,4,6,8,7,5,3,1

 

Are you asking on how to sort a list with custom rules, or the actual code of your sorting rules?

 

I want to know how to sort a list in that order or if there is any code available directly do do the same will be of great help.

 

So to clarify the logic it is this :-

1. Start with old-list of n elements ( index 0 to n-1 ).
2. Want to populate new-list from old-list.
3. Move element old-list[ n-1 ] to new-list[ n / 2 ]
4. Move element old-list[ n-2 ] to new-list[ ( n / 2 ) + 1 ]
5. Move element old-list[ n-3 ] to new-list[ ( n / 2 ) - 1 ]
6. Repeat steps 4 & 5 incrementing the "+/- 1" on each loop until exhaustion of the source list.

Do you agree?

 

Yes thats correct

basically I want the last element of any list to be placed as the middle element of the list and have the second last and third last element to the middle elements left and right.

its a bit hard for me also to explain sorry.

 

This is a bit messy. I've quickly tested it (with [1, 2, 3]). I would recommend testing it more thoroughly yourself though:

Code (CSharp):

1. public List<int> Sort(List<int> source)
2. {
3.     List<int> result = new List<int>(source);
4.     int sign = -1;
5.  
6.     for (int i = 0; i < source.Count; i++)
7.     {
8.         result[(source.Count / 2) + (sign * ((i + 1) / 2))] = source[source.Count - i - 1];
9.         sign = -sign;
10.     }
11.  
12.     return result;
13. }

 

Thanks you DOUG_B this is exactly what I needed perfect works like a charm

I added a simple line in it to make it work for even count list

Code (CSharp):

1.     public List<int> Sort(List<int> source)
2.     {
3.         List<int> result = new List<int>(source);
4.         int sign = -1;
5.  
6.         for (int i = 0; i < source.Count; i++)
7.         {
8.             int index = (source.Count / 2) + (sign * ((i + 1) / 2));
9.             int index2 = (source.Count - i - 1);
10.             if(index < source.Count) // this checks if the index is less the the count if yes then only proceeds.
11.                 result[index] = source[index2];
12.             sign = -sign;
13.         }
14.  
15.         return result;
16.     }

Thank you again