I have the following code, which based on the logic it should work.
I want it to be (4,3,2,1), but at the end of the loop I get t=(4,3,3,4)
Sub try()
Dim t As Variant
t = Array(1, 2, 3, 4)
a = UBound(t)
For k = 0 To a
t(k) = t(a - k)
Next k
End Sub
Any ideas?
You have to use a temporary variable to store the stuff before you make the switch else it will be overwritten.
Is this what you are trying?
Sub try()
Dim t As Variant, tmp As Variant
Dim a As Long, b As Long, i As Long
t = Array(1, 2, 3, 4)
a = UBound(t): b = LBound(t)
For i = 0 To ((a - b) \ 2)
tmp = t(i)
t(i) = t(a)
t(a) = tmp
a = a - 1
Next i
For i = 0 To UBound(t)
Debug.Print t(i)
Next i
End Sub
When you do t(k) = t(a - k) you assign t(a-k) to t(k), but then the value stored in t(k) is lost. You need to temporarily store that in another variable (variable x in the following example), then you can swap the values between t(k) and t(a - k) like this:
Sub try()
Dim t As Variant
Dim x As Variant
Dim b As Integer
t = Array(1, 2, 3, 4)
a = UBound(t)
b = (a - 1) / 2
For k = 0 To b
x = t(k)
t(k) = t(a - k)
t(a - k) = x
Next k
End Sub
Notice that you only need to iterate a number of times that is half of your array size (rounded down) otherwise you'd swap back values again and would end up with the same starting array.
If don't want to delete the original array you can create a copy of the array in reverse creation. See 1D and 2D array subs:
Option Base 1
Sub CopyArrayinReverseColumns1D()
Dim OriginalArr As Variant
Dim newarr As Variant
Dim a As Long
Dim i As Long
OriginalArr = Array(1, 2, 3, 4)
newarr = Array(0, 0, 0, 0)
a = UBound(OriginalArr)
For i = 1 To a
newarr(i) = OriginalArr(a - i + 1)
Debug.Print newarr(i)
Next
End Sub
Sub CopyArrayinReverseColumns2D()
Dim OriginalArr(2, 4) As Variant
Dim newarr(2, 4) As Variant
Dim a As Long
Dim b As Long
Dim i As Long
Dim n As Long
OriginalArr(1, 1) = 65
OriginalArr(1, 2) = 70
OriginalArr(1, 3) = 75
OriginalArr(1, 4) = 80
OriginalArr(2, 1) = 85
OriginalArr(2, 2) = 90
OriginalArr(2, 3) = 95
OriginalArr(2, 4) = 100
a = UBound(OriginalArr, 1)
b = UBound(OriginalArr, 2)
For i = 1 To a
For n = 1 To b
newarr(i, n) = OriginalArr(a - i + 1, n)
Debug.Print newarr(i, n)
Next
Next
End Sub
