squared digit length

am a vb.net beginner anyone please help me solve the following assignment so that i am able to know where to start from

The following process determines the squared digit length of an integer. Take
any integer and add up the squares of its digits. This will give you another
integer. Repeat this procedure until the number you end up with is 1 or 4.
The number of times this process has to be repeated before it gets to one or
4 is the squared digit length. For example, if we start with 48, we get:
4^2 + 8^2 = 80
8^2 + 0^2 = 64
6^2 + 4^2 = 52
5^2 + 2^2 = 29
2^2 + 9^2 = 85
8^2 + 5^2 = 89
8^2 + 9^2 = 145
1^2 + 4^2 + 5^2 = 42
4^2 + 2^2 = 20
2^2 + 0^2 = 4
1
This process shows that the squared digit length of 48 is 10.

Im confused by the very first line in your example - if you add up the squares of the digits in 48, I do get 80 like you do, but surely 4 squared is 16 and 8 squared is 64. How do you get 42 and 82?

And last I checked 42+82 = 124 not 80.

I think I understand the principle of what you are saying but your example doesn't make much sense - can you elaborate?

OK - I understand now - you mean 4^2 and 8^2 not 42 and 82

So how far have you got - it sounds like an assignment for a course is it? I have written a routine to do it but I'd rather help you write your own routine than just give you an answer.

yes keystone_paul is right we are not here to solve your assignment but we will be happy if you do something and ask about the errors :D

Hints: A recursive function fits well for this.

Start with what you've learned so far. If you haven't learned anything then go back to the book.

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Originally Posted by stanav

Hints: A recursive function fits well for this.

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LINQ would do equally good too :D

Quote:

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Originally Posted by stanav

Hints: A recursive function fits well for this.

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I'd be inclined to do this iteratively. I don't really see the advantage in a method calling itself here. I'd go with a Do Until loop.

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I'd be inclined to do this iteratively

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Me too - it took 10 lines of code without recursion, LINQ or anything complicated.

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Originally Posted by keystone_paul

Me too - it took 10 lines of code without recursion, LINQ or anything complicated.

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It took me just 4 lines combined with a LINQ query. But maybe someone would be optimize it better and get a pure LINQ solution.

Since the OP doesn't seem too much interested, lets see what each one of us have been upto. ;)

This is what I was doing:

vb.net Code:

Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
    MsgBox(GetSquaredDigitLength(48))
End Sub
 
Function GetSquaredDigitLength(ByVal num As Double) As Integer
    Dim count As Integer
    Do While num <> 1 AndAlso num <> 4
        count += 1
        num = (From c In num.ToString Select Integer.Parse(c) ^ 2).Sum
    Loop
    Return count
End Function