I have an array of integers and I need to know the index of the largest number (not the actual value, just the index of whichever is highest).
However, if one or more indexes "tie" for the highest value, I need to have all of the indexes that share that high value.
I assume this function would need to return an array (since it could be one or more indexes), but I am not totally sure how to go about getting the more efficient solution.
If this is going to be a common thing you could write your own Extension. You should add some additional sanity/null checking but this will get you started:
Module Extensions
<System.Runtime.CompilerServices.Extension()> Function FindAllIndexes(Of T)(ByVal array() As T, ByVal match As Predicate(Of T)) As Integer()
''//Our return object
Dim Ret As New List(Of Integer)
''//Current array index
Dim I As Integer = -1
''//Infinite loop, break out when we no more matches are found
Do While True
''//Loop for a match based on the last index found, add 1 so we dont keep returning the same value
I = System.Array.FindIndex(array, I + 1, match)
''//If we found something
If I >= 0 Then
''//Append to return object
Ret.Add(I)
Else
''//Otherwise break out of loop
Exit Do
End If
Loop
''//Return our array
Return Ret.ToArray()
End Function
End Module
Then to call it:
Dim ints As Integer() = New Integer() {1, 2, 8, 6, 8, 1, 4}
Dim S = ints.FindAllIndexes(Function(c) c = ints.Max())
''//S now holds 2 and 4
If you are using .NET 3.5, you can use the Max() Extension function to easily find the highest value, and use Where to locate the matching records in your source array.
IList has an IndexOf member, which helps. This code is completely untested, and probably has at least one off-by-one error.
Public Function GetPostionsOfMaxValue(ByVal input() As Integer) As Integer()
Dim ints = New List(Of Integer)(input)
Dim maxval = ints.Max
Dim indexes As New List(Of Integer)
Dim searchStart As Integer = 0
Do Until searchStart >= ints.Count
Dim index = ints.IndexOf(maxval, searchStart)
If index = -1 Then Exit Do
indexes.Add(index)
searchStart = index + 1
Loop
Return indexes.ToArray
End Function
