[RESOLVED] Sorting a multidimensional array

[SavedByGrace]

I am hoping someone can point me in the right direction. I am trying to sort cities by population. The cities are stored in a multidimensional array from a file:

Example (using only 3 of the thousands of cities that are stored in the array):

Dim Cities(2, 2) as string

Cities(0, 0) = "Phoenix" '//City Name
Cities(0, 1) = "Arizona" '//City's State 
Cities(0, 2) = "1469471" '//City's Population

Cities(1, 0) = "New York" '//City Name
Cities(1, 1) = "New York" '//City's State 
Cities(1, 2) = "8244910" '//City's Population

Cities(2, 0) = "Los Angeles" '//City Name
Cities(2, 1) = "California" '//City's State 
Cities(2, 2) = "3819702" '//City's Population

When sorted, I would like for them to be changed into this sequence (highest to lowest):

Cities(0, 0) = "New York" '//City Name
Cities(0, 1) = "New York" '//City's State 
Cities(0, 2) = "8244910" '//City's Population

Cities(1, 0) = "Los Angeles" '//City Name
Cities(1, 1) = "California" '//City's State 
Cities(1, 2) = "3819702" '//City's Population

Cities(2, 0) = "Phoenix" '//City Name
Cities(2, 1) = "Arizona" '//City's State 
Cities(2, 2) = "1469471" '//City's Population

Would like to be able to call a function, sub or routine to sort the cities based on (x, 2) contents of the array (eg. population). I was hoping there might be a simple, straightforward way for doing this.

[SavedByGrace]

After posting this, I did some research and found something that I modified to work with what I am trying to do. I have posted the code below for anyone that may need the same or a similar solution in the future:

Public Class Form1
    Dim Cities(2, 2) As String

    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        Cities(0, 0) = "Phoenix" '//City Name
        Cities(0, 1) = "Arizona" '//City's State 
        Cities(0, 2) = "1469471" '//City's Population

        Cities(1, 0) = "New York" '//City Name
        Cities(1, 1) = "New York" '//City's State 
        Cities(1, 2) = "8244910" '//City's Population

        Cities(2, 0) = "Los Angeles" '//City Name
        Cities(2, 1) = "California" '//City's State 
        Cities(2, 2) = "3819702" '//City's Population
    End Sub

    Public Sub SortCities()
        Dim TempPos As Integer

        For i = 0 To (UBound(Cities) - 1)
            For n = i To UBound(Cities)
                If Cities(n, 2) > Cities(i, 2) Then
                    TempPos = Cities(i, 2)
                    Cities(i, 2) = Cities(n, 2)
                    Cities(n, 2) = TempPos
                End If
            Next
        Next
    End Sub

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        Dim tmp_msg As String = ""
        For i = 0 To UBound(Cities)
            tmp_msg = tmp_msg & Cities(i, 0) & " | " & Cities(i, 1) & " | " & Cities(i, 2) & vbCrLf
        Next

        MsgBox(tmp_msg & "-----------------------------------------")
    End Sub

    Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click
        SortCities()
    End Sub
End Class

[dday9]

This is not the best way to do what you're wanting. What you should do is create a class that will represent your city, then store a collection of cities in a generic list(of <t>). From there you can sort much easier. Here is a quick example:
City class:

'Come on now, they should be on
Option Strict On
Option Explicit On
Public Class City

    'City name, state, and population properties
    Private _name As String
    Public Property Name() As String
        Get
            Return _name
        End Get
        Set(ByVal value As String)
            _name = value
        End Set
    End Property

    Private _state As String
    Public Property State() As String
        Get
            Return _state
        End Get
        Set(ByVal value As String)
            _state = value
        End Set
    End Property

    Private _population As Integer
    Public Property Population() As Integer
        Get
            Return _population
        End Get
        Set(ByVal value As Integer)
            _population = value
        End Set
    End Property

End Class

Form code:

Option Strict On
Option Explicit On
Public Class Form1
    Private cities As New List(Of City)

    Private Sub Form1_Load(sender As System.Object, e As System.EventArgs) Handles MyBase.Load
        'Declare 3 new cities
        Dim pheonix, ny, la As New City

        'Set their properties
        With pheonix
            .Name = "Pheonix"
            .State = "Arizona"
            .Population = 1469471
        End With

        With ny
            .Name = "New York City"
            .State = "New York"
            .Population = 8244910
        End With

        With la
            .Name = "Los Angeles"
            .State = "California"
            .Population = 3819702
        End With

        'Add them to the list
        cities.AddRange({pheonix, ny, la})
    End Sub

    Private Sub btn_Ascending_Click(sender As System.Object, e As System.EventArgs) Handles btn_Ascending.Click
        
        'Sort by population
        cities = cities.OrderBy(Function(x) x.Population).ToList

        'Display results in listbox
        For Each place As City In cities
            ListBox1.Items.Add(place.Name)
        Next

    End Sub

End Class

[SavedByGrace]

Thanks for the suggestion dday9, however, I think you missed the part where I said:

"The cities are stored in a multidimensional array from a file"

and that my example was

"using only 3 of the thousands of cities that are stored in the array"

From what I can tell, If I used your example, I would have to type out the data/code for each of those thousands of cities and the app size would also be over-sized. I'm sure if the list was smaller and more manageable that your solution would likely be a more efficient way to do this but I don't think it is for what I'm trying to achieve.

[Niya]

I have no idea what you mean by this:-

I would have to type out the data/code for each of those thousands of cities and the app size would also be over-sized.

But, a two-dimensional array is not suitable for that kind of data. dday9's example is the right way.

[dday9]

I would have to type out the data/code for each of those thousands of cities and the app size would also be over-sized.

No, not really. The way you'd load the list would be different, yes, but that's all. Here is how I'd load the list if you where using a comma delimited text file:

Option Strict On
Option Explicit On
Public Class Form1
    Private cities As New List(Of City)

    Private Sub load_cities(ByVal file As String, ByVal delimiter As String)
        'New stream reader
        Dim sr As New IO.StreamReader(file)

        'Returns an array of the lines
        Dim str() As String = sr.ReadToEnd.Split({Environment.NewLine}, StringSplitOptions.RemoveEmptyEntries)

        'Loop through all items
        For Each itm As String In str
            'Get each item that's sepearted by the delimiter(in our case a comma)
            Dim newarr() As String = itm.Split({delimiter}, StringSplitOptions.None)

            'Declare a new city
            Dim newcity As New City

            'Set the city's properties
            With newcity
                .Name = newarr(0)
                .State = newarr(1)
                .Population = CInt(newarr(2))
            End With

            'Add it to the list
            cities.Add(newcity)
        Next

    End Sub

    Private Sub Form1_Load(sender As System.Object, e As System.EventArgs) Handles MyBase.Load

        Call load_cities("c:/cities.txt", ",")

    End Sub

    Private Sub Button1_Click(sender As System.Object, e As System.EventArgs) Handles Button1.Click
        'Ascending

        'Clear the listbox
        ListBox1.Items.Clear()

        'Sort by population
        cities = cities.OrderBy(Function(x) x.Population).ToList

        'Display results in listbox
        For Each place As City In cities
            ListBox1.Items.Add(place.Name & " : " & place.Population)
        Next

    End Sub

    Private Sub Button2_Click(sender As System.Object, e As System.EventArgs) Handles Button2.Click
        'Descending

        'Clear the listbox
        ListBox1.Items.Clear()

        'Sort by population
        cities = cities.OrderByDescending(Function(x) x.Population).ToList

        'Display results in listbox
        For Each place As City In cities
            ListBox1.Items.Add(place.Name & " : " & place.Population)
        Next

    End Sub

End Class

Edit - That's assuming you have your format in a: city,state,population where the population can be converted to an integer using CInt. If the data is in a different format, setting newcity's properties would be a bit different(ie - .Name = newarr(2))

[SavedByGrace]

I have no idea what you mean by this:-


But, a two-dimensional array is not suitable for that kind of data. dday9's example is the right way.

What I am trying to say is from the way his example code is structured (mainly the list part - see snipet of his code below), I would have to type 5 lines of code for each city with it's state and population added to the list and since the current file of cities that I am using contains about 5,000 or so cities + states + Populations, to form the list, it would take about 25,000 lines of code to take those cities & data and place them into the code/list that he is suggesting , that doesn't include the declarations of new cities.

A snipet of some of his code that forms the list which I am referring to:

Private cities As New List(Of City)

Private Sub Form1_Load(sender As System.Object, e As System.EventArgs) Handles MyBase.Load
'Declare 3 new cities
Dim pheonix, ny, la As New City

'Set their properties
With pheonix
.Name = "Pheonix"
.State = "Arizona"
.Population = 1469471
End With

[dday9]

What I am trying to say is from the way his example code is structured (mainly the list part - see snipet of his code below), I would have to type 5 lines of code for each city with it's state and population added to the list and since the current file of cities that I am using contains about 5,000 or so cities + states + Populations, to form the list, it would take about 25,000 lines of code to take those cities & data and place them into the code/list that he is suggesting , that doesn't include the declarations of new cities.

A snipet of some of his code that forms the list which I am referring to:

Take a look at my post #6 on loading the data differently.

[SavedByGrace]

No, not really. The way you'd load the list would be different, yes, but that's all. Here is how I'd load the list if you where using a comma delimited text file:

Cool, thanks for the example of how to work with my large list and suggestion.