Android Question Compare Lists

[magarcan]

Hi there!!

I've two lists with Strings as Objects. I've to compare which elements are in both Lits.
I've thoung in make two anidated For loops but don't know if are there a better way to do it.

Any suggestion?

Cheers!

 

[LucaMs]

don't know if are there a better way to do it.

No, because they are of different types.

If they were the same, you could just loop on one list and use IndexOf method of the second one.

 

[stevel05]

I would think the simplest would be something like:

    Dim L1 As List = Array(1,2,3,4,8)
    Dim L2 As List = Array(3,6,7,8)
    Dim Results As List
    Results.Initialize
    
    For Each O As Object In L1
        If L2.IndexOf(O) > -1 Then Results.Add(O)
    Next

    For Each O As Object In Results
        Log(O)
    Next

 

[magarcan]

Here goes my code:

'Compare 2 lists
    For x = 0 To CountryList1.Size-1
        For y = 0 To CountryList2.Size-1
            If (CountryList1.Get(x) == CountryList2.Get(y)) Then
                Log(CountryList1.Get(x) & " are in common")
            End If
        Next
    Next

 

[LucaMs]

I've two lists with Strings as Objects. I've to compare which elements are in both Lits.

1) You cannot compare Strings and Objects

2) You could not compare two objects, you should compare their content (unless you want to know if they are the same object or, better, the same reference to the same object)

3) This is not B4:

==

For x = 0 To CountryList1.Size-1
For y = 0 To CountryList2.Size-1

if both CountryList1 and CountryList2 are lists of strings:

For Each Country As String In CountryList1
    If CountryList2.IndexOf(Country) <> - 1 Then
        Log(Country & " is also in CountryList2")
    End If
Next

 

[LucaMs]

I would prefer lstCountry1 as name

 

[Erel]

If the lists are long then it is better to convert one of them to a Map. List.IndexOf must go over all items until it finds a match - O(n).

Map.ContainsKey on the other hand is very fast - O(1).