BAEL-5646: String permutation examples (#12595) · atcn-java/tutorials@444e46a · GitHub
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BAEL-5646: String permutation examples (eugenp#12595)
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‎algorithms-modules/algorithms-miscellaneous-4/pom.xml‎

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

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

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

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

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

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

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

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

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

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

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

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

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

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