This is the problem:
I have a variable 'Numbers(999) as byte' and I want to make the ten highest of these get into one label(1-10) each.
I know that I can compare each number to all the others, but tthat is about 1000000 operations, and this is quite slow in Visual Basic, so I'd be glad to get help with a faster way!
Sorting the entire array is vast overkill, since you are throwing away 99% of the results. Here's the code.
Dim TopTen(10) as Integer
For i = 1 To UBound(numbers)
if numbers(i) > TopTen(10)
One possible solution would be to make a small database with a table just to hold the numbers. Then pull them out with a 'SORT ASCENDING' SQL statement.
Sort your array with a shellsort, an array of 1000 should take less then a second.
Private sub getHigh(Numbers() as integer, tenHigh() as integer)
Dim tempOrderArray() as integer
Dim I as integer
Redim tempOrderArray(ubound(Numbers)) as integer
' sort your array
IntShellSort Numbers, tempOrderArray
' get the 10 highest into tenHigh
For I = 1 to 10
TenHigh(I) = Numbers(tempOrderArray(I))
Next
End sub
Public Sub IntShellSort(v() As Long, OrderArray() As Integer)
Dim i As Integer
Dim j As Integer
Dim gap As Integer
Dim ArraySize As Integer
Dim Temp As Long
ArraySize = UBound(v)
gap = ArraySize
Do
' if that was the last pass then break
If gap = 1 Then Exit Do
gap = gap / 2
For i = gap To ArraySize
For j = i - gap To 1 Step -gap
If v(OrderArray(j)) < v(OrderArray(j + gap)) Then Exit For
Temp = OrderArray(j)
OrderArray(j) = OrderArray(j + gap)
OrderArray(j + gap) = Temp
Your code seams quite good, but there are som problems.
1. It takes about 10 s and note below 1 that you told me!
2. It does only put zeros in the tenHigh variable!
3. My wonder: why use integer in two places and a long in the third for the same variable, in my version of visual basic that is impossible. I don't know about yours.
If you could correct these problems, I would be happy!
Sorry I didn't even try out my code, your right it does take longer then I thought. Also I forgot a part of it. You'll need this before it's passed to the shellsort. Also the long/integer thing was also a mistake, my bad.
For i = 1 To UBound(numbers)
tempOrderArray(i) = i
Next
You'll be hard pressed to get the sort much faster with VB, the only other things I can suggest is using Jet or using a QuickSort.
Sorting the entire array is vast overkill, since you are throwing away 99% of the results. Here's some code.
Dim TopTen(10) as Integer
For i = 1 To UBound(numbers)
if numbers(i) > TopTen(10) then
for j = 9 to 1 step -1 ' insert the new number into the topten array
if numbers(i) <= TopTen(j) then exit for
TopTen(j+1) = TopTen(j)
next
TopTen(j+1)=numbers(i)
end if
next
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No matter how much faster a sort you get, my approach is better because it's the right algorithm for the job. It runs in 1/10 the time or less, is 10 lines instead of 25, and is a lot simpler. Can't beat that.
I did some benchmarks. On an array of 1000 numbers my approach was less than 1/10 the time and had to do about 1/15 the number of comparisons (1,300 vs. 19,000). (This is with a maximum value to be sorted of 255, the max value makes a big difference, higher is quicker).
By the way, saying "it should take less than a second" ignores the fact that you don't know what kind of machine the other person has. On my work machine (PP200) the shellsort method took 1/10 of a second, my method 1/100. I increased the array size to 30,000 numbers and the new times were 19 seconds and 1/20 of a second.
Sorting the entire array is vast overkill, since you are throwing away 99% of the results. Here's the code.
Dim TopTen(10) as Integer
For i = 1 To UBound(numbers)
if numbers(i) > TopTen(10) then
for j = 9 to 1 step -1 ' insert the new number into the topten array
if numbers(i) <= TopTen(j) then exit for
TopTen(j+1) = TopTen(j)
next
TopTen(j+1)=numbers(i)
end if
next
Thanks Gustav, glad i could help!
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