Solve problems 6, 8, 9 in C#

README.rst

@@ -33,7 +33,7 @@ LivInTheLookingGlass’s Project Euler solutions
 |            | ``msvc``, |br|      |        |               |
 |            | ``pcc``, ``tcc``    |        |               |
 +------------+---------------------+--------+---------------+
-| C#         | .NET 2+             |  2     | |C#i|         |
+| C#         | .NET 2+             |  5     | |C#i|         |
 +------------+---------------------+--------+---------------+
 | JavaScript | Node 12+            |  5     | |JavaScript|  |
 +------------+---------------------+--------+---------------+

csharp/Euler.Test/test.cs

@@ -10,6 +10,9 @@ public static IEnumerable<object[]> Data()
             yield return new object[] { typeof(p0000), 0 };
             yield return new object[] { typeof(p0001), 233168 };
             yield return new object[] { typeof(p0002), 4613732 };
+            yield return new object[] { typeof(p0006), 25164150 };
+            yield return new object[] { typeof(p0008), 23514624000 };
+            yield return new object[] { typeof(p0009), 31875000 };
         }
 
         [Theory]

csharp/Euler/p0006.cs

@@ -0,0 +1,39 @@
+/*
+Project Euler Problem 6
+
+This turned out to be really easy
+
+Problem:
+
+The sum of the squares of the first ten natural numbers is,
+1**2 + 2**2 + ... + 10**2 = 385
+
+The square of the sum of the first ten natural numbers is,
+(1 + 2 + ... + 10)**2 = 55**2 = 3025
+
+Hence the difference between the sum of the squares of the first ten natural
+numbers and the square of the sum is 3025 − 385 = 2640.
+
+Find the difference between the sum of the squares of the first one hundred
+natural numbers and the square of the sum.
+*/
+using System;
+
+namespace Euler
+{
+    public class p0006 : IEuler
+    {
+        public Task<Int64> Answer()
+        {
+            Int64 sum_of_squares = 0,
+                  sum = 0;
+            for (int i = 1; i < 101; i++)
+            {
+                sum += i;
+                sum_of_squares += i * i;
+            }
+            Int64 square_of_sum = sum * sum;
+            return Task.FromResult<Int64>(square_of_sum - sum_of_squares);
+        }
+    }
+}

csharp/Euler/p0008.cs

@@ -0,0 +1,81 @@
+/*
+Project Euler Problem 8
+
+In Python I did this with an iterator, but that is more cumbersome here,
+so I just did it with a loop that slices.
+
+Problem:
+
+The four adjacent digits in the 1000-digit number that have the greatest
+product are 9 × 9 × 8 × 9 = 5832.
+
+73167176531330624919225119674426574742355349194934
+96983520312774506326239578318016984801869478851843
+85861560789112949495459501737958331952853208805511
+12540698747158523863050715693290963295227443043557
+66896648950445244523161731856403098711121722383113
+62229893423380308135336276614282806444486645238749
+30358907296290491560440772390713810515859307960866
+70172427121883998797908792274921901699720888093776
+65727333001053367881220235421809751254540594752243
+52584907711670556013604839586446706324415722155397
+53697817977846174064955149290862569321978468622482
+83972241375657056057490261407972968652414535100474
+82166370484403199890008895243450658541227588666881
+16427171479924442928230863465674813919123162824586
+17866458359124566529476545682848912883142607690042
+24219022671055626321111109370544217506941658960408
+07198403850962455444362981230987879927244284909188
+84580156166097919133875499200524063689912560717606
+05886116467109405077541002256983155200055935729725
+71636269561882670428252483600823257530420752963450
+
+Find the thirteen adjacent digits in the 1000-digit number that have the
+greatest product. What is the value of this product?
+*/
+using System;
+
+namespace Euler
+{
+    public class p0008 : IEuler
+    {
+        private const int MAX = 500;
+        public Task<Int64> Answer()
+        {
+            String str = String.Concat(
+                "73167176531330624919225119674426574742355349194934",
+                "96983520312774506326239578318016984801869478851843",
+                "85861560789112949495459501737958331952853208805511",
+                "12540698747158523863050715693290963295227443043557",
+                "66896648950445244523161731856403098711121722383113",
+                "62229893423380308135336276614282806444486645238749",
+                "30358907296290491560440772390713810515859307960866",
+                "70172427121883998797908792274921901699720888093776",
+                "65727333001053367881220235421809751254540594752243",
+                "52584907711670556013604839586446706324415722155397",
+                "53697817977846174064955149290862569321978468622482",
+                "83972241375657056057490261407972968652414535100474",
+                "82166370484403199890008895243450658541227588666881",
+                "16427171479924442928230863465674813919123162824586",
+                "17866458359124566529476545682848912883142607690042",
+                "24219022671055626321111109370544217506941658960408",
+                "07198403850962455444362981230987879927244284909188",
+                "84580156166097919133875499200524063689912560717606",
+                "05886116467109405077541002256983155200055935729725",
+                "71636269561882670428252483600823257530420752963450"
+            );
+            Int64 answer = 0;
+            for (int i = 0; i < str.Length - 13; i++) {
+                String slice = str.Substring(i, 13);
+                Int64 prod = 1;
+                foreach (char c in slice) {
+                    prod *= c - '0';
+                }
+                if (prod > answer) {
+                    answer = prod;
+                }
+            }
+            return Task.FromResult<Int64>(answer);
+        }
+    }
+}

csharp/Euler/p0009.cs

@@ -0,0 +1,40 @@
+/*
+Project Euler Problem 9
+
+
+
+Problem:
+
+A Pythagorean triplet is a set of three natural numbers, a < b < c, for which,
+a**2 + b**2 = c**2
+
+For example, 3**2 + 4**2 = 9 + 16 = 25 = 5**2.
+
+There exists exactly one Pythagorean triplet for which a + b + c = 1000.
+Find the product abc.
+*/
+using System;
+
+namespace Euler
+{
+    public class p0009 : IEuler
+    {
+        private const int MAX = 500;
+        public Task<Int64> Answer()
+        {
+            for (int c = 3; c < MAX; c++) {
+                int c_square = c * c;
+                for (int b = 2; b < c; b++) {
+                    int b_square = b * b;
+                    for (int a = 1; a < b; a++) {
+                        int a_square = a * a;
+                        if (a_square + b_square == c_square && a + b + c == 1000) {
+                            return Task.FromResult<Int64>(a * b * c);
+                        }
+                    }
+                }
+            }
+            return Task.FromResult<Int64>(0);
+        }
+    }
+}

csharp/Makefile

@@ -18,12 +18,12 @@ help:
 clean:
 	dotnet clean || rm ./*/{bin,obj,TestResults} || echo
 
-test: dependencies
+test:
 ifneq ($(NOT_TERMUX),0)
 	dotnet test --nologo $(cov_args)
 endif
 
-test_%: dependencies
+test_%:
 	$(MAKE) test $(MFLAGS)
 
 dependencies:

docs/csharp/p0006.rst

@@ -0,0 +1,16 @@
+C# Implementation of Problem 6
+==============================
+
+View source code `here on GitHub! <https://github.com/LivInTheLookingGlass/Euler/blob/master/csharp/Euler/p0006.cs>`_
+
+.. csharp:namespace:: Euler
+
+.. csharp:class:: p0006
+
+   .. csharp:inherits:: Euler.IEuler
+
+   .. csharp:method:: Task<Int64> Answer()
+
+.. literalinclude:: ../../csharp/Euler/p0006.cs
+   :language: csharp
+   :linenos:

docs/csharp/p0008.rst

@@ -0,0 +1,16 @@
+C# Implementation of Problem 8
+==============================
+
+View source code `here on GitHub! <https://github.com/LivInTheLookingGlass/Euler/blob/master/csharp/Euler/p0008.cs>`_
+
+.. csharp:namespace:: Euler
+
+.. csharp:class:: p0008
+
+   .. csharp:inherits:: Euler.IEuler
+
+   .. csharp:method:: Task<Int64> Answer()
+
+.. literalinclude:: ../../csharp/Euler/p0008.cs
+   :language: csharp
+   :linenos:

docs/csharp/p0009.rst

@@ -0,0 +1,16 @@
+C# Implementation of Problem 9
+==============================
+
+View source code `here on GitHub! <https://github.com/LivInTheLookingGlass/Euler/blob/master/csharp/Euler/p0009.cs>`_
+
+.. csharp:namespace:: Euler
+
+.. csharp:class:: p0009
+
+   .. csharp:inherits:: Euler.IEuler
+
+   .. csharp:method:: Task<Int64> Answer()
+
+.. literalinclude:: ../../csharp/Euler/p0009.cs
+   :language: csharp
+   :linenos:

docs/index.rst

@@ -109,13 +109,13 @@ This project is divided into several Makefiles, connected by a root Makefile whi
 +-----------+------+------+------+------+------+
 |:prob:`5`  |  |d| |      |      |  |d| |  |d| |
 +-----------+------+------+------+------+------+
-|:prob:`6`  |  |d| |      |  |d| |  |d| |  |d| |
+|:prob:`6`  |  |d| |  |d| |  |d| |  |d| |  |d| |
 +-----------+------+------+------+------+------+
 |:prob:`7`  |  |d| |      |      |  |d| |  |d| |
 +-----------+------+------+------+------+------+
-|:prob:`8`  |  |d| |      |  |d| |  |d| |  |d| |
+|:prob:`8`  |  |d| |  |d| |  |d| |  |d| |  |d| |
 +-----------+------+------+------+------+------+
-|:prob:`9`  |  |d| |      |  |d| |  |d| |  |d| |
+|:prob:`9`  |  |d| |  |d| |  |d| |  |d| |  |d| |
 +-----------+------+------+------+------+------+
 |:prob:`10` |  |d| |      |      |  |d| |  |d| |
 +-----------+------+------+------+------+------+