BAEL-5646: String permutation examples (#12595)

algorithms-modules/algorithms-miscellaneous-4/pom.xml

@@ -13,7 +13,11 @@
         <version>1.0.0-SNAPSHOT</version>
     </parent>
 
-    <dependencies>
+    <properties>
+        <combinatoricslib3.version>3.3.3</combinatoricslib3.version>
+        <commons-collections4.version>4.4</commons-collections4.version>
+    </properties>
+<dependencies>
     <dependency>
         <groupId>com.google.guava</groupId>
         <artifactId>guava</artifactId>
@@ -25,6 +29,16 @@
         <version>${lombok.version}</version>
         <scope>provided</scope>
     </dependency>
-    </dependencies>
+    <dependency>
+        <groupId>com.github.dpaukov</groupId>
+        <artifactId>combinatoricslib3</artifactId>
+        <version>${combinatoricslib3.version}</version>
+    </dependency>
+    <dependency>
+        <groupId>org.apache.commons</groupId>
+        <artifactId>commons-collections4</artifactId>
+        <version>${commons-collections4.version}</version>
+    </dependency>
+</dependencies>
 
 </project>

algorithms-modules/algorithms-miscellaneous-4/src/main/java/com/baeldung/algorithms/stringpermutation/ArrayHelper.java

@@ -0,0 +1,14 @@
+package com.baeldung.algorithms.stringpermutation;
+
+import java.util.List;
+import java.util.stream.Collectors;
+
+public class ArrayHelper {
+
+    private ArrayHelper() {
+    }
+
+    static List<Character> toCharacterList(final String string) {
+        return string.chars().mapToObj(s -> ((char) s)).collect(Collectors.toList());
+    }
+}

algorithms-modules/algorithms-miscellaneous-4/src/main/java/com/baeldung/algorithms/stringpermutation/StringPermutationsApache.java

@@ -0,0 +1,20 @@
+package com.baeldung.algorithms.stringpermutation;
+
+import java.util.Collection;
+import java.util.List;
+import org.apache.commons.collections4.CollectionUtils;
+import org.apache.commons.collections4.iterators.PermutationIterator;
+
+public class StringPermutationsApache {
+
+    public Collection<List<Character>> eagerPermutationWithRepetitions(final String string) {
+        final List<Character> characters = ArrayHelper.toCharacterList(string);
+        return CollectionUtils.permutations(characters);
+    }
+
+    public PermutationIterator<Character> lazyPermutationWithoutRepetitions(final String string) {
+        final List<Character> characters = ArrayHelper.toCharacterList(string);
+        return new PermutationIterator<>(characters);
+    }
+
+}

algorithms-modules/algorithms-miscellaneous-4/src/main/java/com/baeldung/algorithms/stringpermutation/StringPermutationsCombinatoricsLib.java

@@ -0,0 +1,26 @@
+package com.baeldung.algorithms.stringpermutation;
+
+import java.util.List;
+import java.util.stream.Collectors;
+import org.paukov.combinatorics3.Generator;
+import org.paukov.combinatorics3.PermutationGenerator.TreatDuplicatesAs;
+
+public class StringPermutationsCombinatoricsLib {
+
+    public List<List<Character>> permutationWithoutRepetitions(final String string) {
+        List<Character> chars = ArrayHelper.toCharacterList(string);
+        return Generator.permutation(chars)
+            .simple()
+            .stream()
+            .collect(Collectors.toList());
+    }
+
+    public List<List<Character>> permutationWithRepetitions(final String string) {
+        List<Character> chars = ArrayHelper.toCharacterList(string);
+        return Generator.permutation(chars)
+            .simple(TreatDuplicatesAs.IDENTICAL)
+            .stream()
+            .collect(Collectors.toList());
+    }
+
+}

algorithms-modules/algorithms-miscellaneous-4/src/main/java/com/baeldung/algorithms/stringpermutation/StringPermutationsGuava.java

@@ -0,0 +1,18 @@
+package com.baeldung.algorithms.stringpermutation;
+
+import com.google.common.collect.Collections2;
+import java.util.Collection;
+import java.util.List;
+
+public class StringPermutationsGuava {
+
+    public Collection<List<Character>> permutationWithRepetitions(final String string) {
+        final List<Character> characters = ArrayHelper.toCharacterList(string);
+        return Collections2.permutations(characters);
+    }
+public Collection<List<Character>> permutationWithoutRepetitions(final String string) {
+    final List<Character> characters = ArrayHelper.toCharacterList(string);
+    return Collections2.orderedPermutations(characters);
+}
+
+}

algorithms-modules/algorithms-miscellaneous-4/src/test/java/com/baeldung/algorithms/stringpermutation/StringPermutationsApacheUnitTest.java

@@ -0,0 +1,43 @@
+package com.baeldung.algorithms.stringpermutation;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+import java.util.Collection;
+import java.util.List;
+import org.apache.commons.collections4.iterators.PermutationIterator;
+import org.junit.jupiter.api.DisplayName;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.CsvSource;
+
+class StringPermutationsApacheUnitTest {
+
+    @CsvSource({"abc, 6",
+                "hello, 120",
+                "aaaaaa, 720"})
+    @DisplayName("Apache permutation for ")
+    void testPermutationsWithRepetitions(String string, int numberOfPermutations) {
+        StringPermutationsApache permutationGenerator = new StringPermutationsApache();
+        final Collection<List<Character>> permutations = permutationGenerator.eagerPermutationWithRepetitions(string);
+        final int size = permutations.size();
+        assertThat(permutations)
+            .as("\"%s\" should have %d permutation, but had %d", string, numberOfPermutations, size)
+            .hasSize(numberOfPermutations);
+    }
+
+    @ParameterizedTest
+    @CsvSource({"abc, 6",
+        "hello, 120",
+        "aaaaaa, 720"})
+    void testPermutationsWithoutRepetitions(String string, int numberOfPermutations) {
+        StringPermutationsApache permutationGenerator = new StringPermutationsApache();
+        final PermutationIterator<Character> permutations = permutationGenerator.lazyPermutationWithoutRepetitions(string);
+        int size = 0;
+        while (permutations.hasNext()) {
+            permutations.next();
+            ++size;
+        }
+        assertThat(size)
+            .as("\"%s\" should have %d permutation, but had %d", string, numberOfPermutations, size)
+            .isEqualTo(numberOfPermutations);
+    }
+}

algorithms-modules/algorithms-miscellaneous-4/src/test/java/com/baeldung/algorithms/stringpermutation/StringPermutationsCombinatoricsLibUnitTest.java

@@ -0,0 +1,36 @@
+package com.baeldung.algorithms.stringpermutation;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+import java.util.List;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.CsvSource;
+
+class StringPermutationsCombinatoricsLibUnitTest {
+
+    @ParameterizedTest
+    @CsvSource({"abc, 6",
+                "hello, 120",
+                "aaaaaa, 720"})
+    void testPermutationsWithRepetitions(String string, int numberOfPermutations) {
+        StringPermutationsCombinatoricsLib permutationGenerator = new StringPermutationsCombinatoricsLib();
+        final List<List<Character>> permutations = permutationGenerator.permutationWithRepetitions(string);
+        final int size = permutations.size();
+        assertThat(permutations)
+            .as("\"%s\" should have %d permutation, but had %d", string, numberOfPermutations, size)
+            .hasSize(numberOfPermutations);
+    }
+
+    @ParameterizedTest
+    @CsvSource({"abc, 6",
+                "hello, 60",
+                "aaaaaa, 1"})
+    void testPermutationsWithoutRepetitions(String string, int numberOfPermutations) {
+        StringPermutationsCombinatoricsLib permutationGenerator = new StringPermutationsCombinatoricsLib();
+        final List<List<Character>> permutations = permutationGenerator.permutationWithoutRepetitions(string);
+        final int size = permutations.size();
+        assertThat(permutations)
+            .as("\"%s\" should have %d permutation, but had %d", string, numberOfPermutations, size)
+            .hasSize(numberOfPermutations);
+    }
+}

algorithms-modules/algorithms-miscellaneous-4/src/test/java/com/baeldung/algorithms/stringpermutation/StringPermutationsGuavaUnitTest.java

@@ -0,0 +1,38 @@
+package com.baeldung.algorithms.stringpermutation;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+import java.util.Collection;
+import java.util.List;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.CsvSource;
+
+class StringPermutationsGuavaUnitTest {
+
+    @ParameterizedTest
+    @CsvSource({"abc, 6",
+        "hello, 120",
+        "aaaaaa, 720"})
+    void testPermutationsWithRepetitions(String string, int numberOfPermutations) {
+        StringPermutationsGuava permutationGenerator = new StringPermutationsGuava();
+        final Collection<List<Character>> permutations = permutationGenerator.permutationWithRepetitions(string);
+        final int size = permutations.size();
+        assertThat(permutations)
+            .as("\"%s\" should have %d permutation, but had %d", string, numberOfPermutations, size)
+            .hasSize(numberOfPermutations);
+    }
+
+    @ParameterizedTest
+    @CsvSource({"abc, 6",
+        "hello, 60",
+        "aaaaaa, 1"})
+    void testPermutationsWithoutRepetitions(String string, int numberOfPermutations) {
+        StringPermutationsGuava permutationGenerator = new StringPermutationsGuava();
+        final Collection<List<Character>> permutations = permutationGenerator.permutationWithoutRepetitions(string);
+        final int size = permutations.size();
+        assertThat(permutations)
+            .as("\"%s\" should have %d permutation, but had %d", string, numberOfPermutations, size)
+            .hasSize(numberOfPermutations);
+    }
+
+}