iSharkFly-Docs/java-tutorials
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

BAEL-2504 Combinations

Browse Source 
Initial Combinations code.
This commit is contained in:
Chandra Prakash 2019-03-02 07:52:09 -05:00
parent 9f30be503d
commit 7b3da0202e
8 changed files with 209 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

5
algorithms-miscellaneous-1/pom.xml
View File

@ -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>

17
algorithms-miscellaneous-1/src/main/java/com/baeldung/algorithms/combination/ApacheCommonsCombinationGenerator.java Normal file
View File

@ -0,0 +1,17 @@
package com.baeldung.algorithms.combination;
import java.util.Arrays;
import java.util.Iterator;
import org.apache.commons.math3.util.CombinatoricsUtils;
public class ApacheCommonsCombinationGenerator {
public static void main(String[] args) {
Iterator<int[]> iterator = CombinatoricsUtils.combinationsIterator(5, 3);
while (iterator.hasNext()) {
final int[] combination = iterator.next();
System.out.println(Arrays.toString(combination));
}
}
}

13
algorithms-miscellaneous-1/src/main/java/com/baeldung/algorithms/combination/CombinatoricsLibCombinationGenerator.java Normal file
View File

@ -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
View File

@ -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()));
}
}

45
algorithms-miscellaneous-1/src/main/java/com/baeldung/algorithms/combination/IterativeCombinationGenerator.java Normal file
View File

@ -0,0 +1,45 @@
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;
public List<int[]> generate(int n, int r) {
List<int[]> combinations = new ArrayList<>();
int[] combination = new int[r];
for (int i = 0; i < r; i++) {
combination[i] = i;
}
while (combination[r - 1] < n) {
combinations.add(combination.clone());
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));
}
}
}

39
algorithms-miscellaneous-1/src/main/java/com/baeldung/algorithms/combination/SelectionRecursiveCombinationGenerator.java Normal file
View File

@ -0,0 +1,39 @@
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;
public List<int[]> generate(int n, int r) {
List<int[]> combinations = new ArrayList<>();
helper(combinations, new int[r], 0, n - 1, 0);
return combinations;
}
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);
System.out.println(combinations.size());
for (int[] combination : combinations) {
System.out.println(Arrays.toString(combination));
}
}
}

38
algorithms-miscellaneous-1/src/main/java/com/baeldung/algorithms/combination/SetRecursiveCombinationGenerator.java Normal file
View File

@ -0,0 +1,38 @@
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 = 6;
private static final int R = 3;
public List<int[]> generate(int n, int r) {
List<int[]> combinations = new ArrayList<>();
helper(combinations, new int[r], 0, n - 1, 0, r);
return combinations;
}
private void helper(List<int[]> combinations, int data[], int start, int end, int index, int r) {
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, r);
helper(combinations, data, start + 1, end, index, r);
}
}
public static void main(String[] args) {
SetRecursiveCombinationGenerator generator = new SetRecursiveCombinationGenerator();
List<int[]> combinations = generator.generate(N, R);
System.out.println(combinations.size());
for (int[] combination : combinations) {
System.out.println(Arrays.toString(combination));
}
}
}

35
algorithms-miscellaneous-1/src/test/java/com/baeldung/algorithms/combination/CombinationUnitTest.java Normal file
View File

@ -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());
}
}