# Find First and Last Number in a Range of Numbers

Asked by At

Imagine a range of numbers from -133 to +71.

I want to find the first and last numbers in the range that divide by 20: in this case it would be -120 and +60.

I can write a For loop that tests each value and stores the required values:

``````Dim resultFirst, resultLast As Integer
Dim FirstFound As Boolean = False
For a As Integer = -133 To 71
If a Mod 20 = 0 Then
If FirstFound = False Then
resultFirst = a
FirstFound = True
End If
resultLast = a
End If
Next
``````

but I suspect there is a simpler formula.

## 3 Answers On Best Solutions

You can use `Enumerable.Range()` and the LINQ-methods `Where`, `Min` and `Max`

``````Dim resultFirst As Integer
Dim resultLast As Integer
Dim min As Integer = -133
Dim max As Integer = 71
Dim div As Integer = 20

resultFirst = Enumerable.Range(min, max - min + 1).Where(Function(x) x Mod div = 0).Min()
resultLast = Enumerable.Range(min, max - min + 1).Where(Function(x) x Mod div = 0).Max()
`````` On

You can use the following to get the first and last value which is dividable by 20:

``````Dim fromValue As Integer = -133
Dim first As Integer = (fromValue - (fromValue Mod 20)) + IIf(fromValue > 0 And fromValue Mod 20 <> 0, 20, 0)

Dim toValue As Integer = 71
Dim last As Integer = (toValue - (toValue Mod 20)) - IIf(toValue < 0 And toValue Mod 20 <> 0, 20, 0)
``````

You can also create a function using the above formula:

``````Private Function GetResult(ByVal fromInt As Integer, ByVal toInt As Integer, ByVal divider As Integer) As Integer()

'set the real from and to value from parameter.
Dim fromValue As Integer = Math.Min(fromInt, toInt)
Dim toValue As Integer = Math.Max(fromInt, toInt)

'get the first and last number dividable by divider between numbers.
Dim first As Integer = (fromValue - (fromValue Mod divider)) + IIf(fromValue > 0 And fromValue Mod divider <> 0, divider, 0)
Dim last As Integer = (toValue - (toValue Mod divider)) - IIf(toValue < 0 And toValue Mod divider <> 0, divider, 0)

If first > toValue Or last < fromValue Then
Return {}
Else
Return {first, last}
End If
End Function
``````

Some test cases for the above function:

``````GetResult(-133, 71, 20)   '0: -120; 1: 60
GetResult(71, -133, 20)   '0: -120; 1: 60
GetResult(100, 119, 20)   '0: 100;  1: 100
GetResult(-113, -112, 20) 'empty array
GetResult(120, 140, 20)   '0: 120;  1: 140
`````` On

Try this one

``````  Dim s As IEnumerable(Of Integer) =
Enumerable.Range(-133, 133 + 72)

Dim minV As Integer = s.AsEnumerable().Where(Function(n) n Mod 20 = 0).Min(Function(n) n)

Dim maxV As Integer = s.AsEnumerable().Where(Function(n) n Mod 20 = 0).Max(Function(n) n)

Console.WriteLine(minV.ToString() & " " & maxV.ToString())
Console.ReadLine()
``````