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Merge pull request #6460 from chandra1123/BAEL-2504-Combinations 

Bael 2504 combinations
This commit is contained in:
Loredana Crusoveanu 2019-03-06 23:26:00 +02:00 committed by GitHub
parent db6008b167 b796bb0146
commit 6658e92a87
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8 changed files with 255 additions and 1 deletions
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7
algorithms-miscellaneous-1/pom.xml
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@ -39,6 +39,11 @@
<version>${org.assertj.core.version}</version>
<scope>test</scope>
</dependency>
<dependency>
<groupId>com.github.dpaukov</groupId>
<artifactId>combinatoricslib3</artifactId>
<version>3.3.0</version>
</dependency>
</dependencies>
<build>
@ -77,7 +82,7 @@
<commons-math3.version>3.6.1</commons-math3.version>
<org.assertj.core.version>3.9.0</org.assertj.core.version>
<commons-codec.version>1.11</commons-codec.version>
<guava.version>25.1-jre</guava.version>
<guava.version>27.0.1-jre</guava.version>
</properties>
</project>

29
algorithms-miscellaneous-1/src/main/java/com/baeldung/algorithms/combination/ApacheCommonsCombinationGenerator.java Normal file
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@ -0,0 +1,29 @@
package com.baeldung.algorithms.combination;
import java.util.Arrays;
import java.util.Iterator;
import org.apache.commons.math3.util.CombinatoricsUtils;
public class ApacheCommonsCombinationGenerator {
private static final int N = 6;
private static final int R = 3;
/**
* Print all combinations of r elements from a set
* @param n - number of elements in set
* @param r - number of elements in selection
*/
public static void generate(int n, int r) {
Iterator<int[]> iterator = CombinatoricsUtils.combinationsIterator(n, r);
while (iterator.hasNext()) {
final int[] combination = iterator.next();
System.out.println(Arrays.toString(combination));
}
}
public static void main(String[] args) {
generate(N, R);
}
}

13
algorithms-miscellaneous-1/src/main/java/com/baeldung/algorithms/combination/CombinatoricsLibCombinationGenerator.java Normal file
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@ -0,0 +1,13 @@
package com.baeldung.algorithms.combination;
import org.paukov.combinatorics3.Generator;
public class CombinatoricsLibCombinationGenerator {
public static void main(String[] args) {
Generator.combination(0, 1, 2, 3, 4, 5)
.simple(3)
.stream()
.forEach(System.out::println);
}
}

17
algorithms-miscellaneous-1/src/main/java/com/baeldung/algorithms/combination/GuavaCombinationsGenerator.java Normal file
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@ -0,0 +1,17 @@
package com.baeldung.algorithms.combination;
import java.util.Arrays;
import java.util.Set;
import com.google.common.collect.ImmutableSet;
import com.google.common.collect.Sets;
public class GuavaCombinationsGenerator {
public static void main(String[] args) {
Set<Set<Integer>> combinations = Sets.combinations(ImmutableSet.of(0, 1, 2, 3, 4, 5), 3);
System.out.println(combinations.size());
System.out.println(Arrays.toString(combinations.toArray()));
}
}

52
algorithms-miscellaneous-1/src/main/java/com/baeldung/algorithms/combination/IterativeCombinationGenerator.java Normal file
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@ -0,0 +1,52 @@
package com.baeldung.algorithms.combination;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
public class IterativeCombinationGenerator {
private static final int N = 5;
private static final int R = 2;
/**
* Generate all combinations of r elements from a set
* @param n the number of elements in input set
* @param r the number of elements in a combination
* @return the list containing all combinations
*/
public List<int[]> generate(int n, int r) {
List<int[]> combinations = new ArrayList<>();
int[] combination = new int[r];
// initialize with lowest lexicographic combination
for (int i = 0; i < r; i++) {
combination[i] = i;
}
while (combination[r - 1] < n) {
combinations.add(combination.clone());
// generate next combination in lexicographic order
int t = r - 1;
while (t != 0 && combination[t] == n - r + t) {
t--;
}
combination[t]++;
for (int i = t + 1; i < r; i++) {
combination[i] = combination[i - 1] + 1;
}
}
return combinations;
}
public static void main(String[] args) {
IterativeCombinationGenerator generator = new IterativeCombinationGenerator();
List<int[]> combinations = generator.generate(N, R);
System.out.println(combinations.size());
for (int[] combination : combinations) {
System.out.println(Arrays.toString(combination));
}
}
}

53
algorithms-miscellaneous-1/src/main/java/com/baeldung/algorithms/combination/SelectionRecursiveCombinationGenerator.java Normal file
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@ -0,0 +1,53 @@
package com.baeldung.algorithms.combination;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
public class SelectionRecursiveCombinationGenerator {
private static final int N = 6;
private static final int R = 3;
/**
* Generate all combinations of r elements from a set
* @param n - number of elements in input set
* @param r - number of elements to be chosen
* @return the list containing all combinations
*/
public List<int[]> generate(int n, int r) {
List<int[]> combinations = new ArrayList<>();
helper(combinations, new int[r], 0, n - 1, 0);
return combinations;
}
/**
* Choose elements from set by recursing over elements selected
* @param combinations - List to store generated combinations
* @param data - current combination
* @param start - starting element of remaining set
* @param end - last element of remaining set
* @param index - number of elements chosen so far.
*/
private void helper(List<int[]> combinations, int data[], int start, int end, int index) {
if (index == data.length) {
int[] combination = data.clone();
combinations.add(combination);
} else {
int max = Math.min(end, end + 1 - data.length + index);
for (int i = start; i <= max; i++) {
data[index] = i;
helper(combinations, data, i + 1, end, index + 1);
}
}
}
public static void main(String[] args) {
SelectionRecursiveCombinationGenerator generator = new SelectionRecursiveCombinationGenerator();
List<int[]> combinations = generator.generate(N, R);
for (int[] combination : combinations) {
System.out.println(Arrays.toString(combination));
}
System.out.printf("generated %d combinations of %d items from %d ", combinations.size(), R, N);
}
}

50
algorithms-miscellaneous-1/src/main/java/com/baeldung/algorithms/combination/SetRecursiveCombinationGenerator.java Normal file
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@ -0,0 +1,50 @@
package com.baeldung.algorithms.combination;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
public class SetRecursiveCombinationGenerator {
private static final int N = 5;
private static final int R = 2;
/**
* Generate all combinations of r elements from a set
* @param n - number of elements in set
* @param r - number of elements in selection
* @return the list containing all combinations
*/
public List<int[]> generate(int n, int r) {
List<int[]> combinations = new ArrayList<>();
helper(combinations, new int[r], 0, n-1, 0);
return combinations;
}
/**
* @param combinations - List to contain the generated combinations
* @param data - List of elements in the selection
* @param start - index of the starting element in the remaining set
* @param end - index of the last element in the set
* @param index - number of elements selected so far
*/
private void helper(List<int[]> combinations, int data[], int start, int end, int index) {
if (index == data.length) {
int[] combination = data.clone();
combinations.add(combination);
} else if (start <= end) {
data[index] = start;
helper(combinations, data, start + 1, end, index + 1);
helper(combinations, data, start + 1, end, index);
}
}
public static void main(String[] args) {
SetRecursiveCombinationGenerator generator = new SetRecursiveCombinationGenerator();
List<int[]> combinations = generator.generate(N, R);
for (int[] combination : combinations) {
System.out.println(Arrays.toString(combination));
}
System.out.printf("generated %d combinations of %d items from %d ", combinations.size(), R, N);
}
}

35
algorithms-miscellaneous-1/src/test/java/com/baeldung/algorithms/combination/CombinationUnitTest.java Normal file
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@ -0,0 +1,35 @@
package com.baeldung.algorithms.combination;
import static org.junit.jupiter.api.Assertions.assertEquals;
import java.util.List;
import org.junit.Test;
public class CombinationUnitTest {
private static final int N = 5;
private static final int R = 3;
private static final int nCr = 10;
@Test
public void givenSetAndSelectionSize_whenCalculatedUsingSetRecursiveAlgorithm_thenExpectedCount() {
SetRecursiveCombinationGenerator generator = new SetRecursiveCombinationGenerator();
List<int[]> selection = generator.generate(N, R);
assertEquals(nCr, selection.size());
}
@Test
public void givenSetAndSelectionSize_whenCalculatedUsingSelectionRecursiveAlgorithm_thenExpectedCount() {
SelectionRecursiveCombinationGenerator generator = new SelectionRecursiveCombinationGenerator();
List<int[]> selection = generator.generate(N, R);
assertEquals(nCr, selection.size());
}
@Test
public void givenSetAndSelectionSize_whenCalculatedUsingIterativeAlgorithm_thenExpectedCount() {
IterativeCombinationGenerator generator = new IterativeCombinationGenerator();
List<int[]> selection = generator.generate(N, R);
assertEquals(nCr, selection.size());
}
}