GCHQ Puzzle

[Colin Legg]

The BBC website occasionally publishes brain teasers by British GCHQ. See if you can use Excel VBA to solve this puzzle which was published yesterday:

Take the digits 1,2,3 up to 9 in numerical order and put either a plus sign or a minus sign or neither between the digits to make a sum that adds up to 100. For example, one way of achieving this is: 1 + 2 + 34 - 5 + 67 - 8 + 9 = 100, which uses six plusses and minuses. What is the fewest number of plusses and minuses you need to do this?


The solution to the puzzle is on the link.

 

[Special-K99]

Am no VBA expert but this solution sprang to mind
Digits 1 to 9 in row 1, odd numbered columns., A C E etc
Insert a + - or null in even numbered columns
and evaluate the entire row

Sub k1()
Dim arr(3) As String
Dim q As String

arr(1) = ""
arr(2) = "+"
arr(3) = "-"

For i = 1 To 3
For j = 1 To 3
For k = 1 To 3
For l = 1 To 3
For m = 1 To 3
For n = 1 To 3
For o = 1 To 3
For p = 1 To 3

Cells(1, 2) = arr(i)
Cells(1, 4) = arr(j)
Cells(1, 6) = arr(k)
Cells(1, 8) = arr(l)
Cells(1, 10) = arr(m)
Cells(1, 12) = arr(n)
Cells(1, 14) = arr(o)
Cells(1, 16) = arr(p)

q = ""
For r = 1 To 17
q = q & Cells(1, r)
Next r
s = Evaluate(q)
If s = 100 Then Debug.Print q

Next p
Next o
Next n
Next m
Next l
Next k
Next j
Next i
MsgBox "DONE"
End Sub

123+45-67+8-9
123+4-5+67-89
123-45-67+89
123-4-5-6-7+8-9
12+3+4+5-6-7+89
12+3-4+5+67+8+9
12-3-4+5-6+7+89
1+23-4+56+7+8+9
1+23-4+5+6+78-9
1+2+34-5+67-8+9
1+2+3-4+5+6+78+9

 

[chessjess]

oldies but goldies

 

[Colin Legg]

@Special-K99 yes, I used the Evaluate() method to do it too