How to sort a List of arrays by an element at a specified index in the array

Question

I have a list<> of int arrays created like this

List<uint[]> onMinterm = new List<uint[]>();

and it has got 1000 members. Every list members has 3 unsigned integers, I add my arrays just like that

uint[] sayi= new uint[3];    
sayi[0] = 34432; sayi[1] = 63533; sayi[2] = 12;    
onMinterm.Add(sayi);

I want to sort my 1000 list (onMinterm) according to each 3rd member (sayi[2]). List will be sorted in decending order. Sample member should be at the end as its 3rd value is very small like 12.

onMinTerm.OrderByDescending(a => a[2]);. That said, take a look at meta.stackexchange.com/questions/66377/what-is-the-xy-problem — user1726343
– user1726343, Commented May 18, 2015 at 23:40
Design-wise you may want your uint[] to actually be a class or a struct. If you regularly have exactly 3 of somethingand you have that many of them, it's sounding like the stuff in the uint may deserve to have its own identity--i.e., these regularly recurring three values may have some related semantic value that deserves to be named and given their own identity an (possibly, via methods) functionality. — DWright
– DWright, Commented May 18, 2015 at 23:45

Alex · Accepted Answer · 2015-05-18 23:46:06Z

3

I want to sort my 1000 list (onMinterm) according to each 3rd member (sayi[2]). List will be sorted descending.

You can do this, if you are ok with getting an IOrderedEnumerable as the result.

var ordered = onMinterm.OrderByDescending(x => x[2]);

If you want to do an in-place sort:

onMinterm.Sort((x1, x2)=> x2[2].CompareTo(x1[2]));

answered May 18, 2015 at 23:46

Alex

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1 Comment

glenebob Over a year ago

Ah, thanks. I did not know how to do it this way (in place with Comparison delegate).

glenebob · Accepted Answer · 2015-05-19 00:10:38Z

1

You can sort a List<> in place.

    class IntArrayComparer : IComparer<int[]>
    {
      public int Compare(T left, T right)
      {
        return right[2].CompareTo(left[2]);
      }
    }

    myList.Sort(new IntArrayComparer());

edited May 19, 2015 at 0:10

answered May 18, 2015 at 23:48

glenebob

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1 Comment

Alex Over a year ago

Note that this will not result in a descending sort order as OP requested in his question.

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