list.sort，但groupby结束数字

Question

I have a list of items I would like to group by the last two ending numbers, so:

127658
012345
123456
123457
123458
012345

would sort as:

012345
012345
123456
123457
123458
127658

How is this accomplished by overloading list.sort? The output would be very similar to say, an excel autofilter, "ENDS WITH 00"

Answer 1

No overload is needed. Just use a lambda:

list.OrderBy(Function(n) Cint(n.toString().Substring(n.toString().Length-2))).
     ThenBy(Function(n) n)

This is a really polished solution.

---

As Steven Doggart pointed out, you can check for numbers shorter than 2 digits:

list.OrderBy(Function(n) Cint(n.toString().
             Substring(n.toString().Length - Math.Min(n.ToString().Length, 2)))).
     ThenBy(Function(n) n)

---

Or, even simple, using part of MarcinJuraszek 's answer:

list.OrderBy(Function(n) n Mod 100).ThenBy(Function(n) n)

Answer 2

It looks quite easy. Compare function:

Public Shared Function CompareByLastTwo(x As Integer, y As Integer) As Integer
    Return (x Mod 100).CompareTo(y Mod 100)
End Function

And usage:

Dim items as List(Of Integer)

(...)

items.Sort(CompareByLastTwo)

I assumed your items are Integer

Answer 3

This should work (presuming a List(Of String) ):

list = list.Select(Function(num) New With {
               .Num = num,
               .LastTwo = If(num.Length < 2, num, num.Substring(num.Length - 2))
           }).
        OrderBy(Function(x) x.LastTwo).
        ThenBy(Function(x) x.Num).
        Select(Function(x) x.Num).ToList()

If it's a List(Of Int32) the same approach:

intList = intList.
    Select(Function(num) New With {.Num = num, .Str = num.ToString()}).
    Select(Function(x) New With {
        x.Num,
        x.Str,
        .LastTwo = If(x.Str.Length < 2, x.Str, x.Str.Substring(x.Str.Length - 2))
    }).
    OrderBy(Function(x) x.LastTwo).
    ThenBy(Function(x) x.Num).
    Select(Function(x) x.Num).ToList()