sorting an array of integers vb console - arrays

Question

I've written this code to sort an array of 5 numbers in ascending order but I've got an error:
A first chance exception of type 'System.IndexOutOfRangeException' occurred in ConsoleApplication1.exe
Here is the code:
Module Module1
Dim numbers(5) As Integer
Dim flag As Boolean
Dim i As Integer = 0
Sub InputNumbers()
For i = 0 To 4
Console.WriteLine("Input Numbers ")
numbers(i) = Console.ReadLine()
Next i
End Sub
Sub Sort()
Dim temp As Integer
Do
flag = False
For i = 0 To 4
If numbers(i) > numbers(i + 1) Then
temp = numbers(i + 1)
numbers(i + 1) = numbers(i)
numbers(i) = temp
End If
Next i
Loop Until flag = True
End Sub
Sub Output()
For i = 0 To 4
Console.WriteLine("The result is : " & numbers(i))
Next i
End Sub
Sub Main()
InputNumbers()
Sort()
Output()
Console.ReadKey()
End Sub
The error is found here:
For i = 0 To 4
If numbers(i) > numbers(i + 1) Then
temp = numbers(i + 1)
numbers(i + 1) = numbers(i)
numbers(i) = temp
End If
Next i
Can someone please help?

Answer 1

Your array actually contains 6 elements.
'5 represents the upper bond (0 to 5)
Dim numbers(5) as integer
'Declare a single-dimension array of 5 values
Dim numbers(4) As Integer
Then, your statement below is wrong
For i = 0 To 4
If numbers(i) > numbers(i + 1) Then
temp = numbers(i + 1)
numbers(i + 1) = numbers(i)
numbers(i) = temp
End If
Next i
In general, to avoid breaking your code if you ever change the array size, I would use GetUpperBound to get the last index of your array. Furthermore, you cannot make a for to loop up to the last element since in your loop, you look at index: i+1 which will give you an index out of range exception on the last element (That is why I added the "-1" after GetUpperbound.
For i = 0 To numbers.GetUpperBound(0) -1
If numbers(i) > numbers(i + 1) Then
temp = numbers(i + 1)
numbers(i + 1) = numbers(i)
numbers(i) = temp
End If
Next
Ultimately however, the most efficient way to sort your array without hassle is to do this.
Array.Sort(numbers)
For your output function, I would use either GetUpperbound instead of 4 (which will be problematic if the array size is either changed and you forget to change the number) or a For each statement that will adapt itself to any array size without changing that part of the code.
Sub Output()
For each i as integer in numbers
Console.WriteLine("The result is : " & numbers(i))
Next
End Sub

Answer 2

As Sage Pourpre pointed out, where you are using i + 1 to reference the next element in the array, you have to make sure that i + 1 is not greater than the last index of the array. There is more than one way to do that.
Also, with the code in your question, you will have an unending loop because you haven't set the value of flag appropriately. I suggest naming that variable isSorted because it is more meaningful:
Sub Sort()
' perform a bubble sort
Dim temp As Integer
Dim isSorted As Boolean
Do
isSorted = True
For i = 0 To numbers.Length - 2
If numbers(i) > numbers(i + 1) Then
temp = numbers(i + 1)
numbers(i + 1) = numbers(i)
numbers(i) = temp
isSorted = False
End If
Next i
Loop Until isSorted
End Sub