VB.NET Project Euler

[MattP]

Thought I'd take a stab at the Project Euler questions. If anyone has any suggestions on how to improve these I'm all ears.

1. Add all the natural numbers below one thousand that are multiples of 3 or 5.

Private Function Problem1() As Integer
        Return Enumerable.Range(1, 999) _
            .Where(Function(x) {3, 5}.Any(Function(y) x Mod y = 0)) _
            .Sum()
    End Function

[MattP]

2. Find the sum of all the even-valued terms in the Fibonacci sequence which do not exceed four million.

At this point I see that I'm going to need to make some reusable classes for generating numbers as I see Fibonacci and Primes mentioned several times in the first couple of questions.

Here's my generator class.

Public MustInherit Class Yielder(Of T)
    Implements IEnumerable(Of T)
    Implements IEnumerator(Of T)
 
    Private _current As T
 
    Public Sub New()
    End Sub
 
    Protected MustOverride Function [Yield]() As T
 
    Public Function GetEnumerator() As System.Collections.Generic.IEnumerator(Of T) Implements System.Collections.Generic.IEnumerable(Of T).GetEnumerator
        Return Me
    End Function
 
    Public Function GetEnumerator1() As System.Collections.IEnumerator Implements System.Collections.IEnumerable.GetEnumerator
        Return Me
    End Function
 
    Public ReadOnly Property Current As T Implements System.Collections.Generic.IEnumerator(Of T).Current
        Get
            Return _current
        End Get
    End Property
 
    Public ReadOnly Property Current1 As Object Implements System.Collections.IEnumerator.Current
        Get
            Return _current
        End Get
    End Property
 
    Public Function MoveNext() As Boolean Implements System.Collections.IEnumerator.MoveNext
        _current = [Yield]()
        Return True
    End Function
 
    Public Sub Reset() Implements System.Collections.IEnumerator.Reset
        Throw New NotImplementedException()
    End Sub
 
#Region "IDisposable Support"
    Private disposedValue As Boolean ' To detect redundant calls
 
    ' IDisposable
    Protected Overridable Sub Dispose(disposing As Boolean)
        If Not Me.disposedValue Then
            If disposing Then
 
            End If
 
        End If
        Me.disposedValue = True
    End Sub
 
    Public Sub Dispose() Implements IDisposable.Dispose
        Dispose(True)
        GC.SuppressFinalize(Me)
    End Sub
#End Region
 
End Class

My Fibonacci generator class

Public Class Fibonacci
    Inherits Yielder(Of Long)
 
    Private a = 0
    Private b = 1
 
    Protected Overrides Function [Yield]() As Long
        b = a + b
        a = b - a
        Return b
    End Function
 
End Class

Private Function Problem2() As Integer
        Return New Fibonacci() _
            .Where(Function(x) x Mod 2 = 0) _
            .TakeWhile(Function(p) p < 4000000) _
            .Aggregate(Function(sum, x) sum + x)
    End Function

[MattP]

3. What is the largest prime factor of the number 600851475143?

Primes generator class

Public Class Primes
    Inherits Yielder(Of Long)
 
    Dim primes As New List(Of Long)
    Dim prime = 1
 
    Protected Overrides Function [Yield]() As Long
        Do While prime <= Long.MaxValue
            prime += 1
            If prime = 2 Then
                primes.Add(prime)
                Return prime
            End If
            Dim IsPrime = Function(n) primes.TakeWhile(Function(p) p <= Math.Sqrt(n)).FirstOrDefault(Function(p) n Mod p = 0) = 0
            If IsPrime(prime) Then
                primes.Add(prime)
                Return prime
            End If
        Loop
        Return Nothing
    End Function
End Class

Private Function Problem3() As Integer
        Const num = 600851475143
        Return New Primes() _
            .TakeWhile(Function(i) i < Math.Sqrt(num)) _
            .Where(Function(i) num Mod i = 0) _
            .Max()
    End Function

[MattP]

4. Find the largest palindrome made from the product of two 3-digit numbers.

Private Function Problem4() As Integer
        Return (From x In Enumerable.Range(100, 899)
               From y In Enumerable.Range(100, 899)
               Let product = x * y
               Where IsPalindrome(product)
               Order By product Descending
               Select product).First()
    End Function

Public Function IsPalindrome(number As Integer) As Boolean
        Dim digitString = number.ToString()
        Return digitString.SequenceEqual(digitString.Reverse)
    End Function

[MattP]

5. What is the smallest number that is evenly divisible by all of the numbers from 1 to 20?

Private Function Problem5() As Integer
        Return LowestCommonMultiple(Enumerable.Range(1, 20).ToArray)
    End Function
 
    Private Function GreatestCommonDivisor(x As Integer, y As Integer) As Integer
        While y <> 0
            Dim temp = y
            y = x Mod y
            x = temp
        End While
        Return x
    End Function
 
    Private Function LowestCommonMultiple(x As Integer, y As Integer) As Integer
        Return x / GreatestCommonDivisor(x, y) * y
    End Function
 
    Private Function LowestCommonMultiple(divisors As Integer()) As Integer
        Return divisors.Aggregate(1, Function(lcm, n) LowestCommonMultiple(lcm, n))
    End Function

[MattP]

6. Find the difference between the sum of the squares of the first one hundred natural numbers and the square of the sum.

Private Function Problem6() As Integer
        Dim numbers = Enumerable.Range(1, 100)
        Return Math.Pow(numbers.Sum(), 2) - numbers.Aggregate(0, Function(sum, n) sum + Math.Pow(n, 2))
    End Function

[MattP]

7. What is the 10001st prime number?

Score! My Prime class can be reused!

Private Function Problem7() As Integer
        Return New Primes().Take(10001).Last()
    End Function

[MattP]

8. Find the greatest product of five consecutive digits in the 1000-digit number.

Private Function Problem8() As Integer
        Dim chars As Char() = "73167176531330624919225119674426574742355349194934" & _
                              "96983520312774506326239578318016984801869478851843" & _
                              "85861560789112949495459501737958331952853208805511" & _
                              "12540698747158523863050715693290963295227443043557" & _
                              "66896648950445244523161731856403098711121722383113" & _
                              "62229893423380308135336276614282806444486645238749" & _
                              "30358907296290491560440772390713810515859307960866" & _
                              "70172427121883998797908792274921901699720888093776" & _
                              "65727333001053367881220235421809751254540594752243" & _
                              "52584907711670556013604839586446706324415722155397" & _
                              "53697817977846174064955149290862569321978468622482" & _
                              "83972241375657056057490261407972968652414535100474" & _
                              "82166370484403199890008895243450658541227588666881" & _
                              "16427171479924442928230863465674813919123162824586" & _
                              "17866458359124566529476545682848912883142607690042" & _
                              "24219022671055626321111109370544217506941658960408" & _
                              "07198403850962455444362981230987879927244284909188" & _
                              "84580156166097919133875499200524063689912560717606" & _
                              "05886116467109405077541002256983155200055935729725" & _
                              "71636269561882670428252483600823257530420752963450"
 
        Dim digits = Array.ConvertAll(chars, Function(c) CInt(c.ToString()))
 
        Dim maxProduct = 0
        'Dim theDigits As String = String.Empty
 
        For i = 0 To digits.Length - 5
            Dim product = digits(i)
            For j = i + 1 To i + 4
                product *= digits(j)
            Next
 
            If product > maxProduct Then
                maxProduct = product
                'theDigits = String.Join("", chars(i), chars(i + 1), chars(i + 2), chars(i + 3), chars(i + 4))
            End If
        Next
 
        Return maxProduct
    End Function

[MattP]

9. There exists exactly one Pythagorean triplet for which, a + b + c = 1000. Find the product abc.

Private Function Problem9()
        Return (From a In Enumerable.Range(1, 500)
               From b In Enumerable.Range(1, 500)
               Let c = 1000 - a - b
               Where Math.Pow(a, 2) + Math.Pow(b, 2) = Math.Pow(c, 2)
               Select Product = a * b * c).First()
    End Function

[MattP]

10. Find the sum of all the primes below two million.

Private Function Problem10() As Long
        Return New Primes() _
            .TakeWhile(Function(x) x < 2000000) _
            .Aggregate(Function(sum, x) sum + x)
    End Function

[Maven]

Thought I'd take a stab at the Project Euler questions. If anyone has any suggestions on how to improve these I'm all ears.

1. Add all the natural numbers below one thousand that are multiples of 3 or 5.

Private Function Problem1() As Integer
        Return Enumerable.Range(1, 999) _
            .Where(Function(x) {3, 5}.Any(Function(y) x Mod y = 0)) _
            .Sum()
    End Function

Solve for 3n = 1000 to get the highest possible n.
Solve for 5m = 1000 to get the highest possible m.
solve for 15r = 1000 to get the highest possible r.

Where n, m, and r are integers that are always floored. (IE: never round up)

Do the following equation: ans = 3*(n(n+1))/2 + 5 * (m(m+1)/2) - 15 *(r(r+1)/2)


Ans should contain the sum of every natural number that is multiples of 3 or 5.