basically i need to add a name to an array of candidates for an election. the user enters the candidates names, and i want to store them in an array. so far i have this:
Dim CandidateNames(candidates) As String
Dim x As Integer
'entering the names of each candidate so students can vote for them.
For x = 1 To candidates
Console.WriteLine("Enter a candidates name:")
CandidateNames(candidates) = Console.ReadLine()
Next
For x = 0 To candidates - 1
Console.WriteLine(CandidateNames(candidates) & " is candidate " & x)
Next
i want to then output all the names, which is what the second for loop does, but it only outputs the last entered name.
im in my second GCSE year of computer science, having never done any programming before so go easy on me please.
Here is the working code:
Dim candidates as Integer
candidates=5
Dim CandidateNames(candidates) As String
Dim x As Integer
For x = 0 To candidates
Console.WriteLine("Enter a candidates name:")
CandidateNames(x) = Console.ReadLine()
Next
For x = 0 To candidates
Console.WriteLine(CandidateNames(x) & " is candidate ")
Next
In your code, you are not storing and accessing the strings correctly.
There are two issues with your code. The first is with your loop bounds: the first loop is this:
For x = 1 to candidates
And the second loop is this:
For x = 0 to candidates - 1
In .NET, the lower bound for one-dimensional arrays is always 0 (insert rant about .NET array indexing design choices here), so you should be starting from 0 as in the second loop. I can never remember if VB arrays specify the upper bound or the count when you declare them, but conceptually the second is correct for the final index: if you want an array of n items, then it will be indexed from 0 to n - 1.
The second issue is that inside each loop, you are referring to CandidateNames(candidates) instead of CandidateNames(x). Instead of moving through each item in the loop in turn, you are only operating on the last item in the array.
Unless this is for an assignment requiring to use arrays, I'd suggest you consider using List(Of String) instead. Arrays make sense for a more limited set of uses cases, and I don't think this is one of them. Usually, the number of candidates for an election will be variable; with a list, you can have the user enter candidates until they're done, and the list will automatically expand as you go. Then, you can use a For Each loop to write out the contents of the list (though note you could use a For Each loop with an array as well). A list can still be accessed by index like an array.
Related
I have some information in a list (called listLines). Each line below is in a List(Of String).
1|This is just a header
3|This is just a footer
2|3456789|0000000|12312312313|BLUE|1|35.00
2|7891230|0000000|45645645655|BLUE|1|22.00
2|7891230|0000000|45645645658|RED|2|13.00
2|3456789|0000000|12312312316|RED|2|45.00
2|3456789|0000000|12312312317|YELLOW|5|-9.00
2|3456789|0000000|12312312315|ORANGE|3|15.00
2|7891230|0000000|45645645659|YELLOW|5|32.00
2|3456789|0000000|12312312314|GREEN|4|-20.00
2|7891230|0000000|45645645656|GREEN|4|39.00
2|7891230|0000000|45645645657|ORANGE|3|-18.50
I'm doing a listLines.sort() on the list to sort it alphabetically. Below is what I get after the .sort().
1|This is just a header
2|3456789|0000000|12312312313|BLUE|1|35.00
2|3456789|0000000|12312312314|GREEN|4|-20.00
2|3456789|0000000|12312312315|ORANGE|3|15.00
2|3456789|0000000|12312312316|RED|2|45.00
2|3456789|0000000|12312312317|YELLOW|5|-9.00
2|7891230|0000000|45645645655|BLUE|1|22.00
2|7891230|0000000|45645645656|GREEN|4|39.00
2|7891230|0000000|45645645657|ORANGE|3|-18.50
2|7891230|0000000|45645645658|RED|2|13.00
2|7891230|0000000|45645645659|YELLOW|5|32.00
3|This is just a footer
With that said, I need to output this information to a file. I'm able to do this ok. I still have a problem though. There is a sequence number in the above data at position 5 just after the listed colors (RED, BLUE, ETC..) that you can see. It's just before the last value which is a decimal type.
I need to further sort this list, keeping it in alphabetical order since position 2 is an account number and I want to keep the account numbers grouped together. I just want them to be resorted in sequential order based on the sequence number.
I was looking at another thread trying to figure out how I can do this. I found a piece of code like listLines.OrderBy(Function(q) q.Substring(35)).ToArray. I think this would probably help me if this was a fixed length file, it isn't however. I was thinking I can do some kind of .split() to get the 5th piece of information and sort it but then it's going to unalphabetize and mix the lines back up because I don't know how to specify to still keep it alphabetical.
Right now I'm outputting my alphabetical list like below so I can format it with commas and double quotes.
For Each listLine As String In listLines
strPosition = Split(listLine, "|")
Dim i As Integer = 1
Dim iBound As Integer = UBound(strPosition)
Do While (i <= iBound)
strOutputText = strOutputText & Chr(34) & strPosition(i) & Chr(34) & ","
i += 1
Loop
My main question is how do I re-sort after .sort() to then get each account (position1) in sequential order (position 5)? OR EVEN BETTER, how can I do both at the same time?
The List(Of T) class has an overload of the Sort method that takes a Comparison(Of T) delegate. I would suggest that you use that. It allows you to write a method or lambda expression that will take two items and compare them any way you want. In this case, you could do that like this:
Dim items = New List(Of String) From {"1|This Is just a header",
"3|This Is just a footer",
"2|3456789|0000000|12312312313|BLUE|1|35.00",
"2|7891230|0000000|45645645655|BLUE|1|22.00",
"2|7891230|0000000|45645645658|RED|2|13.00",
"2|3456789|0000000|12312312316|RED|2|45.00",
"2|3456789|0000000|12312312317|YELLOW|5|-9.00",
"2|3456789|0000000|12312312315|ORANGE|3|15.00",
"2|7891230|0000000|45645645659|YELLOW|5|32.00",
"2|3456789|0000000|12312312314|GREEN|4|-20.00",
"2|7891230|0000000|45645645656|GREEN|4|39.00",
"2|7891230|0000000|45645645657|ORANGE|3|-18.50"}
items.Sort(Function(x, y)
Dim xParts = x.Split("|"c)
Dim yParts = y.Split("|"c)
'Compare by the first column first.
Dim result = xParts(0).CompareTo(yParts(0))
If result = 0 Then
'Compare by the second column next.
result = xParts(1).CompareTo(yParts(1))
End If
If result = 0 Then
'Compare by the sixth column last.
result = xParts(5).CompareTo(yParts(5))
End If
Return result
End Function)
For Each item In items
Console.WriteLine(item)
Next
If you prefer a named method then do this:
Private Function CompareItems(x As String, y As String) As Integer
Dim xParts = x.Split("|"c)
Dim yParts = y.Split("|"c)
'Compare by the first column first.
Dim result = xParts(0).CompareTo(yParts(0))
If result = 0 Then
'Compare by the second column next.
result = xParts(1).CompareTo(yParts(1))
End If
If result = 0 Then
'Compare by the sixth column last.
result = xParts(5).CompareTo(yParts(5))
End If
Return result
End Function
and this:
items.Sort(AddressOf CompareItems)
Just note that this is rather inefficient because it splits both items on each comparison. That's not a big deal for a small list but, if there were a lot of items, it would be better to split each item once and then sort based on those results.
i have 2 array list, dateListDead and dateListNotMinggu. Both is DateTime List of Array. This is the ilustration of the date value in list of array
The arrayList value
its supposed to remove specific element that exist in other array list.
so far i tried, this code it's not working.
Dim d, x As Integer
For x = 0 To dateListDead.Count - 1
For d = 0 To dateListNotMinggu.Count - 1
If dateListNotMinggu(d) = dateListDead(x) Then
dateListNotMinggu.RemoveAt(d)
End If
Next
Next
the error is : index out of range. how could it be ? i define the parameter of end looping base on arraylist.count -1
The main is that you are using a For loop from the first index to the last index but you don't account for the change of index when you remove a value. If there might be multiple values then you should start and the end rather than the beginning. In that case, removing an item won't affect the indexes of the items you are yet to test. If there can only be one match then you should be exiting the loop when you find one.
Either way, while you don't have to, I would suggest using a For Each loop on the outside. If you want to perform an action for each item in a list then that's exactly what a For Each loop is for. Only use a For loop if you need to use the loop counter for something other than accessing each item in turn.
For multiple matches:
For Each dateDead As Date In dateListDead
For i = dateListNotMinggu.Count - 1 To 0 Step -1
If CDate(dateListNotMinggu(i)) = dateDead Then
dateListNotMinggu.RemoveAt(i)
End If
Next
Next
For a single match:
For Each dateDead As Date In dateListDead
For i = 0 To dateListNotMinggu.Count - 1
If CDate(dateListNotMinggu(i)) = dateDead Then
dateListNotMinggu.RemoveAt(i)
Exit For
End If
Next
Next
Note that I have also cast the Date values as that type for comparison, which is required with Option Strict On. Option Strict is Off by default but you should always turn it On because it will help you write better code by focusing on data types.
Also, the code above would work with a List(Of Date) as well as an ArrayList but the casts would not be required with a List(Of Date). That's one of the advantages of using a generic List(Of T) over an ArrayList, which paces no restrictions on what it can contain.
If you really must use a For loop because that's what your homework assignment says then it would look like this:
For i = 0 To dateListDead.Count - 1
For j = dateListNotMinggu.Count - 1 To 0 Step -1
If CDate(dateListNotMinggu(j)) = CDate(dateListDead(i)) Then
dateListNotMinggu.RemoveAt(j)
End If
Next
Next
and this:
For i = 0 To dateListDead.Count - 1
For j = 0 To dateListNotMinggu.Count - 1
If CDate(dateListNotMinggu(j)) = CDate(dateListDead(i)) Then
dateListNotMinggu.RemoveAt(j)
Exit For
End If
Next
Next
Note that it is convention to use i as a first option for a loop counter, then j for the first nested loop, then k for the second nested loop. You should only use something else if you have good reason to do so. Remember that the loop counter doesn't represent the value in the list but rather its index. That's why you use i for index and not d for date or the like.
EDIT:
As per Jimi's comment below, the way this would usually be tackled is with a simple LINQ query. If you were using LINQ then you definitely wouldn't be using an ArrayList but rather a List(Of Date). In that case, the code would look like this:
dateListNotMinggu = dateListNotMinggu.Except(dateListDead).ToList()
If you were completely insane and wanted to use LINQ and ArrayLists then this would work:
dateListNotMinggu = New ArrayList(dateListNotMinggu.Cast(Of Date)().
Except(dateListDead.Cast(Of Date)()).
ToArray())
Take note that, as I replied in the comments, using LINQ will generate a new list, rather than changing the existing one.
I'm trying to randomize a number in VB.NET 3 times. And each time I randomize a number it should be different from the other two numbers.
For example I have 3 integers. Int1,Int2 and Int3. I will randomize Int1 between 1-10 , and then I will randomize Int2 between 1-10 however the value shouldn't be equal to the value I randomized in Int1 and the same goes for Int3 it shouldn't equal to Int1 and Int2.
I have figured out how to randomize a number, this is the code I'm using:
Dim RndNumber As Random
Dim num,num2 As Integer
RndNumber = New Random
num = RndNumber.Next(1, 11)
num2 = RndNumber.Next(1, 11)
Now I'm stuck on how I make num2 randomize a number between 1-10 that is not equals to num.
I appreciate any help, thanks.
In all the examples, RNG is a random number generator created from the NET Random class:
Private RNG = New Random()
Linq
If you only need two or three, you could loop until the current pick is not in the result set. But this is even simpler using some extension methods:
Dim nums = Enumerable.Range(1, 10).
OrderBy(Function(r) RNG.Next).
Take(3).
ToArray()
This starts with all numbers between 1 and 10, puts them in random order, takes the first 3 and stores them in the nums array. I used the multiline form, breaking after the .s to illustrate the steps.
Just change the range, size/count and Take() element as needed. For instance, for something like a lottery with 5 unique numbers 1-69 (condensed form):
Dim winners = Enumerable.Range(1, 69).OrderBy(Function(r) RNG.Next()).Take(5).ToArray()
Dim powerball = Enumerable.Range(1, 26).OrderBy(Function(r) RNG.Next()).Take(1).First
Since the Powerball can be a repeat of the first numbers, it comes from its own pool. Since we only want one, we dont need an array, just the First().
Manual
It is good to know the logic for these things, so this shows a manual version. This does it differently, by picking and actually checking random values:
' picked value storage
Dim picks As New List(Of Int32)
Dim pick As Int32 ' current candidate
Do
pick = RNG.Next(1, 11)
If picks.Contains(pick) = False Then
picks.Add(pick)
End If
Loop Until picks.Count = 3
Rather than loose vars, this uses a list to hold the picks. This makes it easy to see if the current pick has already been selected. For more than just a few values, use a HashSet(Of Int32) rather than a List for performance.
Random Pairs
To create a random sets of numbers with 2 of each, such as for a matching game, just double up the base pool of values then put them in random order:
' create pool of 2 values each for 1-13
Dim nums = Enumerable.Range(1, 13).ToArray()
' concat the set to make 2 of each value, randomize
Dim pool = nums.Concat(nums).OrderBy(Function(r) RNG.Next).ToArray()
For a manual method you would have to check the count of each value in the loop.
'Use up' Picks
One more variation is when you need a pool of randoms used periodically, but you don't know how many you will need in advance. Examples would be the balls for a BINGO game or a deck of cards.
Rather than a global indexer pointing to the last slot used (or next slot to use), a Stack(Of T) (or a Queue) will "use up" values as you need them:
' create, randomize pool of 100 ints
Dim nums = Enumerable.Range(1, 100).OrderBy(Function(r) RNG.Next).ToArray
' use array to create Stack<T>
Dim shoe As New Stack(Of Int32)(nums)
' same as:
Dim shoe = New Stack(Of Int32)(Enumerable.Range(1, 100).
OrderBy(Function(r) RNG.Next).ToArray())
This starts basically the same with 100 integers, randomized and stored in an array, but there is no Take(n) because we want them all. They values are then stored in a stack collection. Using it:
Console.WriteLine(shoe.Count)
For n As Int32 = 1 To 3
Console.WriteLine("Picked #{0}", shoe.Pop)
Next
Console.WriteLine(shoe.Count)
When you Pop a value it is removed from the collection automatically. If you use a lot of values from the shoe, you will want to check the count to make sure it is not empty.
100
Picked #12
Picked #69
Picked #53
97
After drawing 3 values, the shoe has only 97 values remaining.
Random Notes
In all cases your Random generator should be a form level object which you create once. Never create them in a loop or you will likely get the same value over and over.
The OrderBy(Function(r) RNG.Next) method of randomizing is usually good enough for casual use, but it is inefficient. If you will be randomizing large sets and/or using it frequently you should consider using a proper shuffle such as the Fisher-Yates shuffle shown here.
Is that possible for me to do nested loop in VB with same counter
The code is somehow like this
For a As Integer = 1 to Console.ReadLine
For a = 1 to a
Console.WriteLine("*")
Next
Console.WriteLine()
Next
The program is designed for drawing a triangle of * with just a single variable at all
VB just disallow me to use a in nested loop again
Error: ...Variable 'a' is alreay used by a independent loop.
I have my own usage, can only use 1 variable.
What changing the second FOR loop to a WHILE loop?
For a As Integer = 1 to Console.ReadLine
Do While a <=5
Console.WriteLine("Line: " & a)
Exit Do
Loop
Next
Here's a different idea. You may consider splitting your integer variable into 2 parts 16-bit parts, keep user's input in the upper 16-bits, and current iteration value in the lower 16-bits (you'll need to use WHILE instead of FOR).
In fact, what you need is to start your inner counter by the value of a, if I've understand. And what you are doing is create another loop inside starting by 1.
For a As Integer = 1 to Console.ReadLine
For b As Integer = a to 5
Console.WriteLine("Line: " & a)
Next
Next
You cannot declare another variable with the same name in the same scope. But the inner loop is in the same scope as the outer loop. That's why you get that compiler error.
You can use a different name:
Dim i As Int32
If Int32.TryParse(Console.ReadLine, i) AndAlso i > 0 Then
For a As Integer = 1 To i
For aa = 1 To i
Console.WriteLine("Line: {0} {1}", a, aa)
Next
Next
End If
To draw a triangle, as you describe, you need two variables, like this:
For a As Integer = 1 to Console.ReadLine
For b As Integer = 1 to a
Console.Write("*")
Next
Console.WriteLine()
Next
If you used the same variable in the inner loop, the inner loop would change the value of the variable, which in most cases would not be what you want, and in all cases would be incredibly confusing. For that reason, VB forces you to use a different iterator in each nested For loop.
Thanks in advance for your help. I'm in need of help on writing SSIS script component to delimit single row to multiple rows. There were many helpful blog and post I looked at below:
http://beyondrelational.com/ask/public/questions/1324/ssis-script-component-split-single-row-to-multiple-rows-parent-child-variation.aspx
http://bi-polar23.blogspot.com/2008/06/splitting-delimited-column-in-ssis.html
However, I need a little extra help on coding to complete the project. Basically here's what I want to do.
Input data
ID Item Name
1 Apple01,02,Banana01,02,03
2 Spoon1,2,Fork1,2,3,4
Output data
ParentID ChildID Item Name
1 1 Apple01
1 2 Apple02
1 3 Banana01
1 4 Banana02
1 5 Banana03
2 1 Spoon1
2 2 Spoon2
2 3 Fork1
2 4 Fork2
2 5 Fork3
2 6 Fork4
Below is my attempt to code, but feel free to revise whole if it's illogic. SSIS Asynchronous output is set.
Public Overrides Sub Input0_ProcessInputRow(ByVal Row As Input0Buffer)
Dim posID As Integer, childID As Integer
Dim delimiter As String = ","
Dim txtHolder As String, suffixHolder As String
Dim itemName As String = Row.ItemName
Dim keyField As Integer = Row.ID
If Not (String.IsNullOrEmpty(itemList)) Then
Dim inputListArray() As String = _
itemList.Split(New String() {delimiter}, _
StringSplitOptions.RemoveEmptyEntries)
For Each item As String In inputListArray
Output0Buffer.AddRow()
Output0Buffer.ParentID = keyField
If item.Length >= 3 Then
txtHolder = Trim(item)
Output0Buffer.ItemName = txtHolder
'when item length is less than 3, it's suffix
Else
suffixHolder = Trim(item)
txtHolder = Left(txtHolder.ToString(), Len(txtHolder) _
- Len(suffixHolder)) & suffixHolder.ToString()
Output0Buffer.ItemName = txtHolder
End If
Next
End If
End Sub
The current code produces the following output
ID Item Name
1 Apple01
1 02
1 Banana01
1 02
1 03
2 Spoon1
2 2
2 Fork1
2 2
2 3
2 4
If I come across as pedantic in this response, it is not my intention. Based on the comment "I'm new at coding and having a problem troubleshooting" I wanted to walk through my observations and how I came to them.
Problem analysis
The desire is to split a single row into multiple output rows based on a delimited field associated to the row.
The code as it stands now is generating the appropriate number of rows so you do have the asynchronous part (split) of the script working so that's a plus. What needs to happen is we need to 1) Populate the Child ID column 2) Apply the item prefix to all subsequent row when generating the child items.
I treat most every problem like that. What am I trying to accomplish? What is working? What isn't working? What needs to be done to make it work. Decomposing problems into smaller and smaller problems will eventually result in something you can do.
Code observations
Pasting in the supplied code resulted in an error that itemList was not declared. Based on usage, it seems that it was intended to be itemName.
After fixing that, you should notice the IDE indicating you have 2 unused variables (posID, childID) and that the variable txHolder is used before it's been assigned a value. A null reference exception could result at runtime. My coworker often remarks warnings are errors that haven't grown up yet so my advice to you as a fledgling developer is to pay attention to warnings unless you explicitly expect the compiler to warn you about said scenario.
Getting started
With a choice between solving the Child ID situation versus the name prefix/suffix stuff, I'd start with an easy one, the child id
Generating a surrogate key
That's the fancy title phrase that if you searched on you'd have plenty of hits to ssistalk or sqlis or any of a number of fabulously smart bloggers. Devil of course is knowing what to search on. No where do you ever compute or assign the child id value to the stream which of course is why it isn't showing up there.
We simply need to generate a monotonically increasing number which resets each time the source id changes. I am making an assumption that the inbound ID is unique in the incoming data like a sales invoice number would be unique and we are splitting out the items purchased. However if those IDs were repeated in the dataset, perhaps instead of representing invoice numbers they are salesperson id. Sales Person 1 could have another row in the batch selling vegetables. That's a more complex scenario and we can revisit if that better describes your source data.
There are two parts to generating our surrogate key (again, break problems down into smaller pieces). The first thing to do is make a thing that counts up from 1 to N. You have defined a childId variable to serve this. Initialize this variable (1) and then increment it inside your foreach loop.
Now that we counting, we need to push that value onto the output stream. Putting those two steps together would look like
childID = 1
For Each item As String In inputListArray
Output0Buffer.AddRow()
Output0Buffer.ParentId = keyField
Output0Buffer.ChildId = childID
' There might be VB shorthand for ++
childID = childID + 1
Run the package and success! Scratch the generate surrogate key off the list.
String mashing
I don't know of a fancy term for what needs to be done in the other half of the problem but I needed some title for this section. Given the source data, this one might be harder to get right. You've supplied value of Apple01, Banana01, Spoon1, Fork1. It looks like there's a pattern there (name concatenated with a code) but what it is it? Your code indicates that if it's less than 3, it's a suffix but how do you know what the base is? The first row uses a leading 0 and is two digits long while the second row does not use a leading zero. This is where you need to understand your data. What is the rule for identifying the "code" part of the first row? Some possible algorithms
Force your upstream data providers to provide consistent length codes (I think this has worked once in my 13 years but it never hurts to push back against the source)
Assuming code is always digits, evaluate each character in reverse order testing whether it can be cast to an integer (Handles variable length codes)
Assume the second element in the split array will provide the length of the code. This is the approach you are taking with your code and it actually works.
I made no changes to make the generated item name work beyond fixing the local variables ItemName/itemList. Final code eliminates the warnings by removing PosID and initializing txtHolder to an empty string.
Public Overrides Sub Input0_ProcessInputRow(ByVal Row As Input0Buffer)
Dim childID As Integer
Dim delimiter As String = ","
Dim txtHolder As String = String.Empty, suffixHolder As String
Dim itemName As String = Row.ItemName
Dim keyField As Integer = Row.ID
If Not (String.IsNullOrEmpty(itemName)) Then
Dim inputListArray() As String = _
itemName.Split(New String() {delimiter}, _
StringSplitOptions.RemoveEmptyEntries)
' The inputListArray (our split out field)
' needs to generate values from 1 to N
childID = 1
For Each item As String In inputListArray
Output0Buffer.AddRow()
Output0Buffer.ParentId = keyField
Output0Buffer.ChildId = childID
' There might be VB shorthand for ++
childID = childID + 1
If item.Length >= 3 Then
txtHolder = Trim(item)
Output0Buffer.ItemName = txtHolder
Else
'when item length is less than 3, it's suffix
suffixHolder = Trim(item)
txtHolder = Left(txtHolder.ToString(), Len(txtHolder) _
- Len(suffixHolder)) & suffixHolder.ToString()
Output0Buffer.ItemName = txtHolder
End If
Next
End If
End Sub