Sorry Robert but the last one does not work. All hexes tested were at 3 how distance.
the first code:
3320 3317 3
3320 3418 3
3320 3518 3
3320 3619 3
3320 3620 3
3320 3621 3
3320 3622 3
3320 3522 3
3320 3423 3
3320 3323 3
3320 3223 3
3320 3122 3
3320 3022 3
3320 3021 3
3320 3020 3
3320 3019 3
3320 3118 3
3320 3218 3
the “more efficient”
3320 3317 3
3320 3418 3
3320 3518 3
3320 3619 4
3320 3620 3
3320 3621 3
3320 3622 4
3320 3522 3
3320 3423 3
3320 3323 3
3320 3223 3
3320 3122 3
3320 3022 4
3320 3021 3
3320 3020 3
3320 3019 4
3320 3118 3
3320 3218 3
That is interesting. Thanks for feedback. The old saying: [quote]better is the enemy of good.[/quote]
One more try and I will let this rest. Again an attempt to be more efficient. There is one line of code added to the working code previously submitted. I am throwing this back up because Enric you seem to have written the code to test these things.
NEW LINE
// the diagonals
If Abs(rowA - rowB) = Abs(colA - colB) \\ 2 Then Return jump + Abs(colA - colB)
COMPLETE CODE
[code]Public Function CheckDistance(fromHex As String, toHex As String) As Integer
Var hexA, hexB As Integer
hexA = fromHex.Val
hexB = toHex.Val
Var colA, colB, rowA, rowB As Integer
colA = hexA \ 100
colB = hexB \ 100
rowA = hexA Mod 100
rowB = hexB Mod 100
Var jump As Integer = 0
Do
loopCount = loopCount + 1
If colA = colB And rowA = rowB Then Return jump + 0
If colA = colB Then Return jump + Abs(rowA - rowB)
If rowA = rowB Then Return jump + Abs(colA - colB)
If colA Mod 2 = 0 And rowA = rowB + 1 Then Return jump + Abs(colA - colB)
If colA Mod 2 = 1 And rowA = rowB - 1 Then Return jump + Abs(colA - colB)
// the diagonals
If Abs(rowA - rowB) = Abs(colA - colB) \ 2 Then Return jump + Abs(colA - colB)
jump = jump + 1
If colA Mod 2 = 0 And rowA > rowB And colA > colB Then
rowA = rowA - 1
colA = colA - 1
Continue
End If
If colA Mod 2 = 0 And rowA > rowB And colA < colB Then
rowA = rowA - 1
colA = colA + 1
Continue
End If
If colA Mod 2 = 1 And rowA < rowB And colA < colB Then
rowA = rowA + 1
colA = colA + 1
Continue
End If
If colA Mod 2 = 1 And rowA < rowB And colA > colB Then
rowA = rowA + 1
colA = colA - 1
Continue
End If
If Abs(colA - colB) > Abs(rowA - rowB) Then
// change column
If colA < colB Then colA = colA + 1 Else colA = colA - 1
Else
// change row
If rowA < rowB Then rowA = rowA + 1 Else rowA = rowA - 1
End If
Loop[/code]
Yes Robert, with the last added line of code the method works.
I cannot appreciate any difference in execution time but, as you said, is more efficient.
Again, thank you.
I couldn’t get this algorithm question out of my mind. My solution was clever but still a little elaborate. I have thought more about the issue.
[code]Public Function CheckDistance(fromHex As String, toHex As String) As Integer
Var hexA, hexB As Integer
hexA = fromHex.Val
hexB = toHex.Val
Var colA, colB, rowA, rowB As Integer
colA = hexA \ 100
colB = hexB \ 100
rowA = hexA Mod 100
rowB = hexB Mod 100
Var colDelta, rowDelta As Integer
colDelta = Abs(colA - colB)
rowDelta = Abs(rowA - rowB)
Return colDelta + Max(0, (rowDelta - (colDelta + 1) \ 2))[/code]
Thanks Robert, it seems to work and it’s quite more efficient.
Well, Enric pointed out to me later that it (my May 1 response) was incorrect for many situations. This one is more tested. 
[code]Public Function CheckDistance(fromHex As String, toHex As String) As Integer
Var hexA, hexB As Integer
hexA = fromHex.Val
hexB = toHex.Val
Var colA, colB, rowA, rowB As Integer
colA = hexA \ 100
colB = hexB \ 100
rowA = hexA Mod 100
rowB = hexB Mod 100
Var deltaCol, deltaRow As Integer
deltaCol = Abs(colA - colB)
deltaRow = Abs(rowA - rowB)
// Special cases
If colA = colB Then Return deltaRow
If rowA = rowB Then Return deltaCol
If colA Mod 2 = 1 Then // odd column
If rowA > rowB Then
Return Max(0, deltaRow - (deltaCol \ 2)) + deltaCol
Else
Return Max(0, deltaRow - ((deltaCol + 1) \ 2)) + deltaCol
End If
Else
If rowA > rowB Then
Return Max(0, deltaRow - ((deltaCol + 1) \ 2)) + deltaCol
Else
Return Max(0, deltaRow - (deltaCol \ 2)) + deltaCol
End If
End If[/code]
Thanks again Robert, will check it.