| Clover coverage report - PLT Utilities Test Coverage (plt-20120304-r5436) |
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| Source file | Conditionals | Statements | Methods | TOTAL | |||||||||||||||
| PermutationIterator.java | 0% | 0% | 0% | 0% |
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| 1 | /*BEGIN_COPYRIGHT_BLOCK* | |
| 2 | ||
| 3 | PLT Utilities BSD License | |
| 4 | ||
| 5 | Copyright (c) 2007-2010 JavaPLT group at Rice University | |
| 6 | All rights reserved. | |
| 7 | ||
| 8 | Developed by: Java Programming Languages Team | |
| 9 | Rice University | |
| 10 | http://www.cs.rice.edu/~javaplt/ | |
| 11 | ||
| 12 | Redistribution and use in source and binary forms, with or without modification, are permitted | |
| 13 | provided that the following conditions are met: | |
| 14 | ||
| 15 | - Redistributions of source code must retain the above copyright notice, this list of conditions | |
| 16 | and the following disclaimer. | |
| 17 | - Redistributions in binary form must reproduce the above copyright notice, this list of | |
| 18 | conditions and the following disclaimer in the documentation and/or other materials provided | |
| 19 | with the distribution. | |
| 20 | - Neither the name of the JavaPLT group, Rice University, nor the names of the library's | |
| 21 | contributors may be used to endorse or promote products derived from this software without | |
| 22 | specific prior written permission. | |
| 23 | ||
| 24 | THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR | |
| 25 | IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND | |
| 26 | FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDERS AND | |
| 27 | CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL | |
| 28 | DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, | |
| 29 | DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER | |
| 30 | IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT | |
| 31 | OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. | |
| 32 | ||
| 33 | *END_COPYRIGHT_BLOCK*/ | |
| 34 | ||
| 35 | package edu.rice.cs.plt.iter; | |
| 36 | ||
| 37 | import java.util.Iterator; | |
| 38 | ||
| 39 | /** | |
| 40 | * Enumerates all permutations of the given list. Behavior is undefined if | |
| 41 | * the given list changes during iteration. The size of the enumeration, where | |
| 42 | * the original list has size n, is n! (and is thus guaranteed to be >= 1). The order of the | |
| 43 | * results is lexicographical, assuming each element of the original list is taken to | |
| 44 | * lexicographically precede all of its successors. (Thus, the original list is | |
| 45 | * the first to be returned, and a reversed list is the last.) Of course, due to the | |
| 46 | * factorial complexity of enumerating all permutations, this class is probably not suitable | |
| 47 | * for applications in which n is unbounded (or just intractably large). | |
| 48 | * | |
| 49 | * @param <T> The element type of the permuted lists; note that {@code next()} returns | |
| 50 | * {@code Iterable<T>}s, not {@code T}s. | |
| 51 | */ | |
| 52 | public class PermutationIterator<T> extends ReadOnlyIterator<Iterable<T>> { | |
| 53 | ||
| 54 | private final Iterable<? extends T> _original; | |
| 55 | private final Iterator<? extends T> _elements; | |
| 56 | private T _element; | |
| 57 | private int _elementIndex; | |
| 58 | private Iterator<Iterable<T>> _restPermutations; | |
| 59 | ||
| 60 | 0 | public PermutationIterator(Iterable<? extends T> original) { |
| 61 | 0 | _original = original; |
| 62 | 0 | _elements = _original.iterator(); |
| 63 | // _element is initialized later | |
| 64 | 0 | _elementIndex = -1; |
| 65 | ||
| 66 | // to deal with the empty case, we set _restPermutations appropriately | |
| 67 | 0 | if (IterUtil.isEmpty(_original)) { |
| 68 | 0 | _restPermutations = SingletonIterator.<Iterable<T>>make(EmptyIterable.<T>make()); |
| 69 | } | |
| 70 | 0 | else { _restPermutations = EmptyIterator.make(); } |
| 71 | } | |
| 72 | ||
| 73 | 0 | public boolean hasNext() { return _restPermutations.hasNext() || _elements.hasNext(); } |
| 74 | ||
| 75 | 0 | public Iterable<T> next() { |
| 76 | // in the empty case, _restPermutations contians a single empty list | |
| 77 | 0 | if (IterUtil.isEmpty(_original)) { return _restPermutations.next(); } |
| 78 | else { | |
| 79 | 0 | if (!_restPermutations.hasNext()) { |
| 80 | 0 | _element = _elements.next(); // exception occurs if !elements.hasNext() |
| 81 | 0 | _elementIndex++; |
| 82 | 0 | _restPermutations = new PermutationIterator<T>(makeRest(_elementIndex)); |
| 83 | // restPermutations must now haveNext() | |
| 84 | } | |
| 85 | 0 | return new ComposedIterable<T>(_element, _restPermutations.next()); |
| 86 | } | |
| 87 | } | |
| 88 | ||
| 89 | 0 | private Iterable<T> makeRest(int skipIndex) { |
| 90 | 0 | Iterable<T> result = EmptyIterable.make(); |
| 91 | 0 | int i = 0; |
| 92 | 0 | for (T e : _original) { |
| 93 | 0 | if (i != skipIndex) { result = new ComposedIterable<T>(result, e); } |
| 94 | 0 | i++; |
| 95 | } | |
| 96 | 0 | return result; |
| 97 | } | |
| 98 | ||
| 99 | /** Call the constructor (allows {@code T} to be inferred) */ | |
| 100 | 0 | public static <T> PermutationIterator<T> make(Iterable<? extends T> original) { |
| 101 | 0 | return new PermutationIterator<T>(original); |
| 102 | } | |
| 103 | } |
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