Solve p20, p34, p76 in Java

LivInTheLookingGlass · Aug 11, 2024 · 4d336bb · 4d336bb
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diff --git a/README.rst b/README.rst
@@ -73,7 +73,7 @@ Olivia's Project Euler Solutions
 |            |                          |        | |CodeQL| |br|     |
 |            |                          |        | |C#-lint|         |
 +------------+--------------------------+--------+-------------------+
-| Java       | Java 8+                  | 14     | |Javai| |br|      |
+| Java       | Java 8+                  | 17     | |Javai| |br|      |
 |            |                          |        | |Ja-Cov| |br|     |
 |            |                          |        | |CodeQL| |br|     |
 |            |                          |        | |Java-lint|       |

diff --git a/docs/index.rst b/docs/index.rst
@@ -107,7 +107,7 @@ Problems Solved
 +-----------+------------+------------+------------+------------+------------+------------+------------+
 |:prob:`19` |            |            |            |            |            |:py-d:`0019`|:rs-d:`0019`|
 +-----------+------------+------------+------------+------------+------------+------------+------------+
-|:prob:`20` |:c-d:`0020` |:cp-d:`0020`|:cs-d:`0020`|            |:js-d:`0020`|:py-d:`0020`|:rs-d:`0020`|
+|:prob:`20` |:c-d:`0020` |:cp-d:`0020`|:cs-d:`0020`|:ja-d:`0020`|:js-d:`0020`|:py-d:`0020`|:rs-d:`0020`|
 +-----------+------------+------------+------------+------------+------------+------------+------------+
 |:prob:`21` |            |            |            |            |            |:py-d:`0021`|            |
 +-----------+------------+------------+------------+------------+------------+------------+------------+
@@ -133,7 +133,7 @@ Problems Solved
 +-----------+------------+------------+------------+------------+------------+------------+------------+
 |:prob:`33` |            |            |            |            |            |:py-d:`0033`|            |
 +-----------+------------+------------+------------+------------+------------+------------+------------+
-|:prob:`34` |:c-d:`0034` |:cp-d:`0034`|:cs-d:`0034`|            |:js-d:`0034`|:py-d:`0034`|:rs-d:`0034`|
+|:prob:`34` |:c-d:`0034` |:cp-d:`0034`|:cs-d:`0034`|:ja-d:`0034`|:js-d:`0034`|:py-d:`0034`|:rs-d:`0034`|
 +-----------+------------+------------+------------+------------+------------+------------+------------+
 |:prob:`35` |            |            |            |            |            |:py-d:`0035`|            |
 +-----------+------------+------------+------------+------------+------------+------------+------------+
@@ -195,7 +195,7 @@ Problems Solved
 +-----------+------------+------------+------------+------------+------------+------------+------------+
 |:prob:`74` |            |            |            |            |            |:py-d:`0074`|            |
 +-----------+------------+------------+------------+------------+------------+------------+------------+
-|:prob:`76` |:c-d:`0076` |:cp-d:`0076`|:cs-s:`0076`|            |:js-s:`0076`|:py-d:`0076`|:rs-d:`0076`|
+|:prob:`76` |:c-d:`0076` |:cp-d:`0076`|:cs-s:`0076`|:ja-s:`0076`|:js-s:`0076`|:py-d:`0076`|:rs-d:`0076`|
 +-----------+------------+------------+------------+------------+------------+------------+------------+
 |:prob:`77` |            |            |            |            |            |:py-d:`0077`|            |
 +-----------+------------+------------+------------+------------+------------+------------+------------+

diff --git a/docs/java/p0015.rst b/docs/java/p0015.rst
@@ -3,6 +3,14 @@ Java Implementation of Problem 15
 
 View source code :source:`java/src/main/java/euler/p0015.java`
 
+Includes
+--------
+
+- `Mathematics.java <./math.html>`_
+
+Problem Solution
+----------------
+
 .. java:type:: public class p0015 implements IEuler
 
    .. java:method:: Object answer()

diff --git a/docs/java/p0020.rst b/docs/java/p0020.rst
@@ -0,0 +1,14 @@
+Java Implementation of Problem 20
+=================================
+
+View source code :source:`java/src/main/java/euler/p0020.java`
+
+.. java:type:: public class p0020 implements IEuler
+
+   .. java:method:: Object answer()
+
+    :return: The answer to Project Euler problem 20
+
+.. literalinclude:: ../../java/src/main/java/euler/p0020.java
+   :language: java
+   :linenos:
diff --git a/docs/java/p0022.rst b/docs/java/p0022.rst
@@ -3,6 +3,13 @@ Java Implementation of Problem 22
 
 View source code :source:`java/src/main/java/euler/p0022.java`
 
+Includes
+--------
+
+- `Utilities.java <./utils.html>`_
+
+Problem Solution
+----------------
 .. java:type:: public class p0022 implements IEuler
 
    .. java:method:: Object answer()

diff --git a/docs/java/p0034.rst b/docs/java/p0034.rst
@@ -0,0 +1,14 @@
+Java Implementation of Problem 34
+=================================
+
+View source code :source:`java/src/main/java/euler/p0034.java`
+
+.. java:type:: public class p0034 implements IEuler
+
+   .. java:method:: Object answer()
+
+    :return: The answer to Project Euler problem 34
+
+.. literalinclude:: ../../java/src/main/java/euler/p0034.java
+   :language: java
+   :linenos:
diff --git a/docs/java/p0076.rst b/docs/java/p0076.rst
@@ -0,0 +1,14 @@
+Java Implementation of Problem 76
+=================================
+
+View source code :source:`java/src/main/java/euler/p0076.java`
+
+.. java:type:: public class p0076 implements IEuler
+
+   .. java:method:: Object answer()
+
+    :return: The answer to Project Euler problem 76
+
+.. literalinclude:: ../../java/src/main/java/euler/p0076.java
+   :language: java
+   :linenos:
diff --git a/java/README.rst b/java/README.rst
@@ -87,5 +87,8 @@ Problems Solved
 -  ☒ `15 <./src/main/java/p0015.java>`__
 -  ☒ `16 <./src/main/java/p0016.java>`__
 -  ☒ `17 <./src/main/java/p0017.java>`__
+-  ☒ `20 <./src/main/java/p0020.java>`__
 -  ☒ `22 <./src/main/java/p0022.java>`__
+-  ☒ `34 <./src/main/java/p0034.java>`__
+-  ☒ `76 <./src/main/java/p0076.java>`__
 -  ☒ `836 <./src/main/java/p0836.java>`__
diff --git a/java/src/main/java/euler/p0020.java b/java/src/main/java/euler/p0020.java
@@ -0,0 +1,47 @@
+/*
+Project Euler Problem 34
+
+This ended up being a filtering problem. The problem with my solution is that I
+am not satisfied with my filter at all. I feel like there is a more efficient
+way to go about it.
+
+Problem:
+
+145 is a curious number, as 1! + 4! + 5! = 1 + 24 + 120 = 145.
+
+Find the sum of all numbers which are equal to the sum of the factorial of
+their digits.
+
+Note: as 1! = 1 and 2! = 2 are not sums they are not included.
+*/
+package euler;
+
+public class p0020 implements IEuler {
+    @Override
+    public Object answer() {
+        long[] numbers = new long[10];
+        long ten17 = 100000000000000000L;
+        numbers[0] = 1;
+        for (byte i = 2; i <= 100; i++) {
+            for (byte j = 0; j < 10; j++) {
+                numbers[j] *= i;
+            }
+            for (byte j = 0; j < 9; j++) {
+                if (numbers[j] > ten17) {
+                    numbers[j + 1] += numbers[j] / ten17;
+                    numbers[j] %= ten17;
+                }
+            }
+        }
+        long answer = 0;
+        long power = 1;
+        for (byte i = 0; i < 19; i++) {
+            for (byte j = 0; j < 10; j++) {
+                long value = numbers[j] / power;
+                answer += value % 10;
+            }
+            power *= 10;
+        }
+        return (short) answer;
+    }
+}
diff --git a/java/src/main/java/euler/p0022.java b/java/src/main/java/euler/p0022.java
@@ -30,7 +30,9 @@ public Object answer() {
         int answer = 0;
         String[] names;
         try {
-            names = Utilities.getDataFileText("p0022_names.txt").replace("\"", "").split(",", 0);
+            names = Utilities.getDataFileText("p0022_names.txt")
+                             .replace("\"", "")
+                             .split(",", 0);
         } catch (IOException e) {
             return null;
         }

diff --git a/java/src/main/java/euler/p0034.java b/java/src/main/java/euler/p0034.java
@@ -0,0 +1,35 @@
+/*
+Project Euler Problem 34
+
+This ended up being a filtering problem. The problem with my solution is that I
+am not satisfied with my filter at all. I feel like there is a more efficient
+way to go about it.
+
+Problem:
+
+145 is a curious number, as 1! + 4! + 5! = 1 + 24 + 120 = 145.
+
+Find the sum of all numbers which are equal to the sum of the factorial of
+their digits.
+
+Note: as 1! = 1 and 2! = 2 are not sums they are not included.
+*/
+package euler;
+
+import euler.lib.Mathematics;
+
+public class p0034 implements IEuler {
+    @Override
+    public Object answer() {
+        int answer = 0;
+        for (int x = 10; x < 100000; x += 1) {
+            String xs = Integer.toString(x);
+            int sum = 0;
+            for (byte i = 0; i < xs.length(); i += 1)
+                sum += (int) Mathematics.factorial(xs.charAt(i) - '0');
+            if (sum == x)
+                answer += x;
+        }
+        return (short) answer;
+    }
+}
diff --git a/java/src/main/java/euler/p0076.java b/java/src/main/java/euler/p0076.java
@@ -0,0 +1,50 @@
+/*
+Project Euler Problem 76
+
+I ended up having to do this iteratively, which I'm not super happy with. I feel like there is almost certainly a
+closed-form solution to this, but I was unable to figure it out.
+
+Problem:
+
+It is possible to write five as a sum in exactly six different ways:
+
+4 + 1
+3 + 2
+3 + 1 + 1
+2 + 2 + 1
+2 + 1 + 1 + 1
+1 + 1 + 1 + 1 + 1
+
+How many different ways can one hundred be written as a sum of at least two
+positive integers?
+*/
+package euler;
+
+public class p0076 implements IEuler {
+    @Override
+    public Object answer() {
+        byte idx, sum = 100;
+        int answer = 0;
+        byte[] counts = new byte[101];
+        counts[2] = 100;
+        while (counts[100] == 0) {
+            counts[2] += 2;
+            if (sum >= 100) {
+                answer += (100 + counts[2] - sum) / 2;
+                idx = 2;
+                do {
+                    counts[idx] = 0;
+                    idx += 1;
+                    counts[idx] += idx;
+                    sum = 0;
+                    for (byte i = (byte) (idx - 1); i < 101; i += 1)
+                        sum += counts[i];
+                } while (sum > 100);
+            }
+            sum = 0;
+            for (byte i = 0; i < 101; i += 1)
+                sum += counts[i];
+        }
+        return answer;
+    }
+}
diff --git a/java/src/test/java/EulerTest.java b/java/src/test/java/EulerTest.java
@@ -27,10 +27,10 @@ static Stream<Object[]> data() throws IOException {
                 new Object[] { p0015.class, false, Utilities.getAnswer(15) },
                 new Object[] { p0016.class, false, Utilities.getAnswer(16) },
                 new Object[] { p0017.class, false, Utilities.getAnswer(17) },
-                // new Object[]{p0020.class, false, Utilities.getAnswer(20)},
+                new Object[] { p0020.class, false, Utilities.getAnswer(20) },
                 new Object[] { p0022.class, false, Utilities.getAnswer(22) },
-                // new Object[]{p0034.class, false, Utilities.getAnswer(34)},
-                // new Object[]{p0076.class, true, Utilities.getAnswer(76)},
+                new Object[] { p0034.class, false, Utilities.getAnswer(34) },
+                new Object[] { p0076.class, true, Utilities.getAnswer(76) },
                 new Object[] { p0836.class, false, Utilities.getAnswer(836) });
     }