/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.commons.math4.util;
import java.util.Iterator;
import java.util.Comparator;
import org.apache.commons.math4.exception.DimensionMismatchException;
import org.apache.commons.math4.exception.MathIllegalArgumentException;
import org.apache.commons.math4.exception.OutOfRangeException;
import org.apache.commons.math4.util.Combinations;
import org.apache.commons.math4.util.CombinatoricsUtils;
import org.junit.Assert;
import org.junit.Test;
/**
* Tests for the {@link Combinations} class.
*
*/
public class CombinationsTest {
@Test
public void testAccessor1() {
final int n = 5;
final int k = 3;
Assert.assertEquals(n, new Combinations(n, k).getN());
}
@Test
public void testAccessor2() {
final int n = 5;
final int k = 3;
Assert.assertEquals(k, new Combinations(n, k).getK());
}
@Test
public void testLexicographicIterator() {
checkLexicographicIterator(new Combinations(5, 3));
checkLexicographicIterator(new Combinations(6, 4));
checkLexicographicIterator(new Combinations(8, 2));
checkLexicographicIterator(new Combinations(6, 1));
checkLexicographicIterator(new Combinations(3, 3));
checkLexicographicIterator(new Combinations(1, 1));
checkLexicographicIterator(new Combinations(1, 0));
checkLexicographicIterator(new Combinations(0, 0));
checkLexicographicIterator(new Combinations(4, 2));
checkLexicographicIterator(new Combinations(123, 2));
}
@Test(expected=DimensionMismatchException.class)
public void testLexicographicComparatorWrongIterate1() {
final int n = 5;
final int k = 3;
final Comparator<int[]> comp = new Combinations(n, k).comparator();
comp.compare(new int[] {1}, new int[] {0, 1, 2});
}
@Test(expected=DimensionMismatchException.class)
public void testLexicographicComparatorWrongIterate2() {
final int n = 5;
final int k = 3;
final Comparator<int[]> comp = new Combinations(n, k).comparator();
comp.compare(new int[] {0, 1, 2}, new int[] {0, 1, 2, 3});
}
@Test(expected=OutOfRangeException.class)
public void testLexicographicComparatorWrongIterate3() {
final int n = 5;
final int k = 3;
final Comparator<int[]> comp = new Combinations(n, k).comparator();
comp.compare(new int[] {1, 2, 5}, new int[] {0, 1, 2});
}
@Test(expected=OutOfRangeException.class)
public void testLexicographicComparatorWrongIterate4() {
final int n = 5;
final int k = 3;
final Comparator<int[]> comp = new Combinations(n, k).comparator();
comp.compare(new int[] {1, 2, 4}, new int[] {-1, 1, 2});
}
@Test
public void testLexicographicComparator() {
final int n = 5;
final int k = 3;
final Comparator<int[]> comp = new Combinations(n, k).comparator();
Assert.assertEquals(1, comp.compare(new int[] {1, 2, 4},
new int[] {1, 2, 3}));
Assert.assertEquals(-1, comp.compare(new int[] {0, 1, 4},
new int[] {0, 2, 4}));
Assert.assertEquals(0, comp.compare(new int[] {1, 3, 4},
new int[] {1, 3, 4}));
}
/**
* Check that iterates can be passed unsorted.
*/
@Test
public void testLexicographicComparatorUnsorted() {
final int n = 5;
final int k = 3;
final Comparator<int[]> comp = new Combinations(n, k).comparator();
Assert.assertEquals(1, comp.compare(new int[] {1, 4, 2},
new int[] {1, 3, 2}));
Assert.assertEquals(-1, comp.compare(new int[] {0, 4, 1},
new int[] {0, 4, 2}));
Assert.assertEquals(0, comp.compare(new int[] {1, 4, 3},
new int[] {1, 3, 4}));
}
@Test
public void testEmptyCombination() {
final Iterator<int[]> iter = new Combinations(12345, 0).iterator();
Assert.assertTrue(iter.hasNext());
final int[] c = iter.next();
Assert.assertEquals(0, c.length);
Assert.assertFalse(iter.hasNext());
}
@Test
public void testFullSetCombination() {
final int n = 67;
final Iterator<int[]> iter = new Combinations(n, n).iterator();
Assert.assertTrue(iter.hasNext());
final int[] c = iter.next();
Assert.assertEquals(n, c.length);
for (int i = 0; i < n; i++) {
Assert.assertEquals(i, c[i]);
}
Assert.assertFalse(iter.hasNext());
}
/**
* Verifies that the iterator generates a lexicographically
* increasing sequence of b(n,k) arrays, each having length k
* and each array itself increasing.
*
* @param c Combinations.
*/
private void checkLexicographicIterator(Combinations c) {
final Comparator<int[]> comp = c.comparator();
final int n = c.getN();
final int k = c.getK();
int[] lastIterate = null;
long numIterates = 0;
for (int[] iterate : c) {
Assert.assertEquals(k, iterate.length);
// Check that the sequence of iterates is ordered.
if (lastIterate != null) {
Assert.assertTrue(comp.compare(iterate, lastIterate) == 1);
}
// Check that each iterate is ordered.
for (int i = 1; i < iterate.length; i++) {
Assert.assertTrue(iterate[i] > iterate[i - 1]);
}
lastIterate = iterate;
++numIterates;
}
// Check the number of iterates.
Assert.assertEquals(CombinatoricsUtils.binomialCoefficient(n, k),
numIterates);
}
@Test
public void testCombinationsIteratorFail() {
try {
new Combinations(4, 5).iterator();
Assert.fail("expecting MathIllegalArgumentException");
} catch (MathIllegalArgumentException ex) {
// ignored
}
try {
new Combinations(-1, -2).iterator();
Assert.fail("expecting MathIllegalArgumentException");
} catch (MathIllegalArgumentException ex) {
// ignored
}
}
}