Six friends Al, Ben, Cal, Dan, Elmer and Frank want to cross a bridge. It is a very dark night but there is only one torch between the six of them. The bridge is narrow so that only two people at a time can cross it. It is known that:
Al takes exactly 1 minute to cross the bridge.
Ben takes exactly 2 minutes to cross the bridge.
Cal takes exactly 4 minutes to cross the bridge.
Dan takes exactly 7 minutes to cross the bridge.
Elmer takes exactly 12 minutes to cross the bridge.
Frank takes exactly 19 minutes to cross the bridge.
When two people cross the bridge, they do so with the pace of the slower person.
Determine the minimum amount of time it will take all six friends to cross the bridge.
Successively better times:
AB A AC A AD A AE A AF 48
AB A AC A AD A AF A AE 48
AB A AC A AD A EF B AB 39
AB A AC A AD B EF A AB 39
AB A AC A EF B AB A AD 39
AB A AC A EF B AD A AB 39
AB A AC B EF A AB A AD 39
AB A AC B EF A AD A AB 39
AB A AD A AC A EF B AB 39
AB A AD A AC B EF A AB 39
AB A AD A EF B AB A AC 39
AB A AD A EF B AC A AB 39
AB A AD B EF A AB A AC 39
AB A AD B EF A AC A AB 39
AB A CD B AB A EF B AB 38
AB A CD B AB B EF A AB 38
AB A EF B AB A CD B AB 38
AB A EF B AB B CD A AB 38
AB B CD A AB A EF B AB 38
AB B CD A AB B EF A AB 38
AB B EF A AB A CD B AB 38
AB B EF A AB B CD A AB 38
where the pairs of letters are across and single letters back. Each is followed by the time.
DefDbl A-Z
Dim crlf$, leftMemb(6), rightMemb(6), totTime, minTime, h$
Private Sub Form_Load()
Form1.Visible = True
leftMemb(0) = 6
leftMemb(1) = 1
leftMemb(2) = 2
leftMemb(3) = 4
leftMemb(4) = 7
leftMemb(5) = 12
leftMemb(6) = 19
rightMemb(0) = 0
minTime = 9999
Text1.Text = ""
crlf = Chr$(13) + Chr$(10)
xfer
Text1.Text = Text1.Text & crlf & " done"
End Sub
Sub xfer()
For i = 1 To 5
If leftMemb(i) > 0 Then
rightMemb(i) = leftMemb(i)
leftMemb(i) = 0
For j = i + 1 To 6
If leftMemb(j) > 0 Then
rightMemb(j) = leftMemb(j)
leftMemb(j) = 0
leftMemb(0) = leftMemb(0) - 2
rightMemb(0) = rightMemb(0) + 2
totTime = totTime + rightMemb(j)
h = h + Mid("ABCDEF", i, 1) + Mid("ABCDEF", j, 1) + " "
If rightMemb(0) = 6 Then
If totTime <= minTime Then
minTime = totTime
Text1.Text = Text1.Text & h & minTime & crlf
End If
Else
For k = 1 To 6
If rightMemb(k) > 0 Then
leftMemb(k) = rightMemb(k)
rightMemb(k) = 0
leftMemb(0) = leftMemb(0) + 1
rightMemb(0) = rightMemb(0) - 1
totTime = totTime + leftMemb(k)
h = h + Mid("ABCDEF", k, 1) + " "
xfer
h = Left(h, Len(h) - 2)
leftMemb(0) = leftMemb(0) - 1
rightMemb(0) = rightMemb(0) + 1
rightMemb(k) = leftMemb(k)
leftMemb(k) = 0
totTime = totTime - rightMemb(k)
End If
Next k
End If
h = Left(h, Len(h) - 3)
totTime = totTime - rightMemb(j)
leftMemb(0) = leftMemb(0) + 2
rightMemb(0) = rightMemb(0) - 2
leftMemb(j) = rightMemb(j)
rightMemb(j) = 0
End If
Next
leftMemb(i) = rightMemb(i)
rightMemb(i) = 0
End If
Next
End Sub
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Posted by Charlie
on 2016-10-10 15:45:39 |
Wouldda, Coudda, Shouldda done it by computer
