add project euler.net TriplicateNumbers problem

java-dsa/pom.xml

@@ -1,7 +1,7 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <project xmlns="http://maven.apache.org/POM/4.0.0"
-         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
-         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
     <modelVersion>4.0.0</modelVersion>
 
     <groupId>io.giovannymassuia</groupId>
@@ -21,6 +21,12 @@
             <version>5.10.0</version>
             <scope>test</scope>
         </dependency>
+        <dependency>
+            <groupId>org.junit.jupiter</groupId>
+            <artifactId>junit-jupiter-params</artifactId>
+            <version>5.10.0</version>
+            <scope>test</scope>
+        </dependency>
     </dependencies>
 
     <build>
@@ -41,10 +47,10 @@
                         <disable>true</disable>
                     </consoleOutputReporter>
                     <statelessTestsetInfoReporter
-                            implementation="org.apache.maven.plugin.surefire.extensions.junit5.JUnit5StatelessTestsetInfoTreeReporterUnicode"/>
+                        implementation="org.apache.maven.plugin.surefire.extensions.junit5.JUnit5StatelessTestsetInfoTreeReporterUnicode"/>
                 </configuration>
             </plugin>
         </plugins>
     </build>
 
-</project>
+</project>

java-dsa/src/main/java/io/giovannymassuia/eulernet/triplicatenumber/TriplicateNumbers.java

@@ -0,0 +1,19 @@
+package io.giovannymassuia.eulernet.triplicatenumber;
+
+/**
+ * A triplicate number is a positive integer such that, after repeatedly removing three consecutive
+ * identical digits from it, all its digits can be removed.</p>
+ *
+ * <p>
+ * For example, the integer 122555211 is a triplicate number:
+ * </p>
+ * <p>
+ * 122[555]211 -> 1[222]11 -> [111] -> .
+ * </p>
+ * On the other hand, neither 663633 nor 9990 are triplicate numbers.
+ */
+public interface TriplicateNumbers {
+
+    boolean isTriplicate(long number);
+
+}

java-dsa/src/main/java/io/giovannymassuia/eulernet/triplicatenumber/TriplicateNumbersNaive.java

@@ -0,0 +1,32 @@
+package io.giovannymassuia.eulernet.triplicatenumber;
+
+public class TriplicateNumbersNaive implements TriplicateNumbers {
+
+    @Override
+    public boolean isTriplicate(long number) {
+        String numberString = String.valueOf(number);
+//        char[] numbers = numberString.toCharArray();
+//        Map<Character, Integer> counter = new HashMap<>();
+//
+//        for (char n : numbers) {
+//            counter.merge(n, 1, Integer::sum);
+//        }
+
+        int len = numberString.length() / 3;
+
+        for (int i = 0; i < len; i++) {
+            for (int j = 0; j <= 9; j++) {
+                String x = String.valueOf(j).repeat(3);
+                if (numberString.contains(x)) {
+                    numberString = numberString.replace(x, "");
+                }
+
+                if (numberString.isEmpty()) {
+                    return true;
+                }
+            }
+        }
+
+        return numberString.isEmpty();
+    }
+}

java-dsa/src/main/java/io/giovannymassuia/eulernet/triplicatenumber/TriplicateNumbersStack.java

@@ -0,0 +1,75 @@
+package io.giovannymassuia.eulernet.triplicatenumber;
+
+import java.util.HashMap;
+import java.util.Map;
+import java.util.Stack;
+
+public class TriplicateNumbersStack implements TriplicateNumbers {
+
+    @Override
+    public boolean isTriplicate(long number) {
+        // 122555244411L
+        // [1] <-> [2] <-> [5] <-> [2] <-> [4] <-> [1]
+        //  1       2       3       1       3       2
+        return solutionWithTuple(number) && solutionWithMap(number);
+    }
+
+    private boolean solutionWithMap(long number) {
+        Stack<Character> stack = new Stack<>();
+        Map<Character, Integer> counter = new HashMap<>();
+
+        char[] numbers = String.valueOf(number).toCharArray();
+
+        stack.push(numbers[0]);
+        counter.put(numbers[0], 1);
+
+        for (int i = 1; i < numbers.length; i++) {
+            char curr = numbers[i];
+
+            counter.merge(curr, 1, Integer::sum);
+
+            if (!stack.isEmpty() && stack.peek() == curr) {
+                if (counter.get(curr) == 3) {
+                    stack.pop();
+                    counter.put(curr, 0);
+                }
+            } else {
+                stack.push(curr);
+            }
+        }
+
+        return stack.isEmpty();
+    }
+
+    private boolean solutionWithTuple(long number) {
+        Stack<Tuple> stack = new Stack<>();
+        char[] numbers = String.valueOf(number).toCharArray();
+
+        for (char n : numbers) {
+            if (!stack.isEmpty() && stack.peek().c == n) {
+                if (++stack.peek().count == 3) {
+                    stack.pop();
+                }
+                continue;
+            }
+            stack.push(Tuple.of(n));
+        }
+
+        return stack.isEmpty();
+    }
+
+    static class Tuple {
+
+        char c;
+        int count = 1;
+
+        Tuple(char c) {
+            this.c = c;
+        }
+
+        static Tuple of(char c) {
+            return new Tuple(c);
+        }
+    }
+
+}

java-dsa/src/test/java/io/giovannymassuia/eulernet/triplicatenumber/TriplicateNumbersTest.java

@@ -0,0 +1,38 @@
+package io.giovannymassuia.eulernet.triplicatenumber;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import java.util.stream.Stream;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.Arguments;
+import org.junit.jupiter.params.provider.MethodSource;
+
+class TriplicateNumbersTest {
+
+    TriplicateNumbers triplicateNumbersNaive = new TriplicateNumbersNaive();
+    TriplicateNumbers triplicateNumbersStack = new TriplicateNumbersStack();
+
+    @ParameterizedTest
+    @MethodSource("buildInputs")
+    void isTriplicateNaive(long input, boolean expect) {
+        assertEquals(triplicateNumbersNaive.isTriplicate(input), expect);
+    }
+
+    @ParameterizedTest
+    @MethodSource("buildInputs")
+    void isTriplicateStack(long input, boolean expect) {
+        assertEquals(triplicateNumbersStack.isTriplicate(input), expect);
+    }
+
+    private static Stream<Arguments> buildInputs() {
+        return Stream.of(
+            Arguments.of(122555211L, true),
+            Arguments.of(663633L, false),
+            Arguments.of(9990L, false),
+            Arguments.of(122555244411L, true),
+            Arguments.of(122255522211L, true),
+            Arguments.of(122344433211L, true),
+            Arguments.of(411433314111444L, false)
+        );
+    }
+}