CODEWITHSUNDEEP
vb.netmultidimensional-array
djv
djv

Reputation: 15782

How do I find the min and max value of a multidimensional array?

I want to find the minimum and maximum values of this array. At some point it is set to (512, 512) UShorts. A For loop would be very time consuming for this many points and am looking for something cleaner. SelectMany occurred to me but I don't know how to implement it.

Dim usResult As UShort(,)

edit: I have tried

Dim minValue As UShort = UShort.MaxValue
Dim maxValue As UShort = UShort.MinValue
Dim sw As New Stopwatch()
sw.Start()
For i As Integer = 0 To 511 Step 1
    For j As Integer = 0 To 511 Step 1
        minValue = Math.Min(usResult(i, j), minValue)
        maxValue = Math.Max(usResult(i, j), maxValue)
    Next
Next
sw.Stop()
Console.WriteLine(sw.ElapsedMilliseconds)
' This takes 2 to 3 milliseconds

Upvotes: 4

Views: 7502

Answers (2)

Meta-Knight
Meta-Knight

Reputation: 17875

The simplest way to get min/max of a multi-dimensional array is by doing this:

Dim max As UShort = usResult.Cast(Of UShort).Max()
Dim min As UShort = usResult.Cast(Of UShort).Min()

It doesn't offer better performance than a for loop though. You would need to use a specialized data structure that keeps elements sorted, or keeps track of min/max elements, to get better performance.

Upvotes: 3

xpda
xpda

Reputation: 15813

A for loop might be much less time-consuming than you expect. Try timing it to see how long it takes to find the min and max 100,000 times with nested loops.

Upvotes: 1

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