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1 | /* |
2 | Copyright (c) Marshall Clow 2011-2012. | |
3 | ||
4 | Distributed under the Boost Software License, Version 1.0. (See accompanying | |
5 | file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) | |
6 | */ | |
7 | ||
8 | /// \file is_permutation.hpp | |
9 | /// \brief Is a sequence a permutation of another sequence | |
10 | /// \author Marshall Clow | |
11 | ||
12 | #ifndef BOOST_ALGORITHM_IS_PERMUTATION11_HPP | |
13 | #define BOOST_ALGORITHM_IS_PERMUTATION11_HPP | |
14 | ||
15 | #include <algorithm> // for std::find_if, count_if, mismatch | |
16 | #include <utility> // for std::pair | |
17 | #include <functional> // for std::equal_to | |
18 | #include <iterator> | |
19 | ||
20 | #include <boost/range/begin.hpp> | |
21 | #include <boost/range/end.hpp> | |
22 | #include <boost/utility/enable_if.hpp> | |
23 | #include <boost/type_traits/is_same.hpp> | |
24 | ||
25 | namespace boost { namespace algorithm { | |
26 | ||
27 | /// \cond DOXYGEN_HIDE | |
28 | namespace detail { | |
29 | template <typename Predicate, typename Iterator> | |
30 | struct value_predicate { | |
31 | value_predicate ( Predicate p, Iterator it ) : p_ ( p ), it_ ( it ) {} | |
32 | ||
33 | template <typename T1> | |
34 | bool operator () ( const T1 &t1 ) const { return p_ ( *it_, t1 ); } | |
35 | private: | |
36 | Predicate p_; | |
37 | Iterator it_; | |
38 | }; | |
39 | ||
40 | // Preconditions: | |
41 | // 1. The sequences are the same length | |
42 | // 2. Any common elements on the front have been removed (not necessary for correctness, just for performance) | |
43 | template< class ForwardIterator1, class ForwardIterator2, class BinaryPredicate > | |
44 | bool is_permutation_inner ( ForwardIterator1 first1, ForwardIterator1 last1, | |
45 | ForwardIterator2 first2, ForwardIterator2 last2, | |
46 | BinaryPredicate p ) { | |
47 | // for each unique value in the sequence [first1,last1), count how many times | |
48 | // it occurs, and make sure it occurs the same number of times in [first2, last2) | |
49 | for ( ForwardIterator1 iter = first1; iter != last1; ++iter ) { | |
50 | value_predicate<BinaryPredicate, ForwardIterator1> pred ( p, iter ); | |
51 | ||
52 | /* For each value we haven't seen yet... */ | |
53 | if ( std::find_if ( first1, iter, pred ) == iter ) { | |
54 | std::size_t dest_count = std::count_if ( first2, last2, pred ); | |
55 | if ( dest_count == 0 || dest_count != (std::size_t) std::count_if ( iter, last1, pred )) | |
56 | return false; | |
57 | } | |
58 | } | |
59 | ||
60 | return true; | |
61 | } | |
62 | ||
63 | template< class ForwardIterator1, class ForwardIterator2, class BinaryPredicate> | |
64 | bool is_permutation_tag ( ForwardIterator1 first1, ForwardIterator1 last1, | |
65 | ForwardIterator2 first2, ForwardIterator2 last2, | |
66 | BinaryPredicate p, | |
67 | std::forward_iterator_tag, std::forward_iterator_tag ) { | |
68 | ||
69 | // Skip the common prefix (if any) | |
70 | while ( first1 != last1 && first2 != last2 && p ( *first1, *first2 )) { | |
71 | ++first1; | |
72 | ++first2; | |
73 | } | |
74 | if ( first1 != last1 && first2 != last2 ) | |
75 | return boost::algorithm::detail::is_permutation_inner ( first1, last1, first2, last2, | |
76 | std::equal_to<typename std::iterator_traits<ForwardIterator1>::value_type> ()); | |
77 | return first1 == last1 && first2 == last2; | |
78 | } | |
79 | ||
80 | template <class RandomAccessIterator1, class RandomAccessIterator2, class BinaryPredicate> | |
81 | bool is_permutation_tag ( RandomAccessIterator1 first1, RandomAccessIterator1 last1, | |
82 | RandomAccessIterator2 first2, RandomAccessIterator2 last2, | |
83 | BinaryPredicate p, | |
84 | std::random_access_iterator_tag, std::random_access_iterator_tag ) { | |
85 | // Cheap check | |
86 | if ( std::distance ( first1, last1 ) != std::distance ( first2, last2 )) | |
87 | return false; | |
88 | // Skip the common prefix (if any) | |
89 | while ( first1 != last1 && first2 != last2 && p ( *first1, *first2 )) { | |
90 | ++first1; | |
91 | ++first2; | |
92 | } | |
93 | ||
94 | if ( first1 != last1 && first2 != last2 ) | |
95 | return is_permutation_inner (first1, last1, first2, last2, p); | |
96 | return first1 == last1 && first2 == last2; | |
97 | } | |
98 | ||
99 | } | |
100 | /// \endcond | |
101 | ||
102 | /// \fn is_permutation ( ForwardIterator1 first, ForwardIterator1 last, ForwardIterator2 first2, BinaryPredicate p ) | |
103 | /// \brief Tests to see if the sequence [first,last) is a permutation of the sequence starting at first2 | |
104 | /// | |
105 | /// \param first1 The start of the input sequence | |
106 | /// \param last1 One past the end of the input sequence | |
107 | /// \param first2 The start of the second sequence | |
108 | /// \param p The predicate to compare elements with | |
109 | /// | |
110 | /// \note This function is part of the C++2011 standard library. | |
111 | template< class ForwardIterator1, class ForwardIterator2, class BinaryPredicate > | |
112 | bool is_permutation ( ForwardIterator1 first1, ForwardIterator1 last1, | |
113 | ForwardIterator2 first2, BinaryPredicate p ) | |
114 | { | |
115 | // Skip the common prefix (if any) | |
116 | std::pair<ForwardIterator1, ForwardIterator2> eq = std::mismatch (first1, last1, first2, p); | |
117 | first1 = eq.first; | |
118 | first2 = eq.second; | |
119 | if ( first1 != last1 ) { | |
120 | // Create last2 | |
121 | ForwardIterator2 last2 = first2; | |
122 | std::advance ( last2, std::distance (first1, last1)); | |
123 | return boost::algorithm::detail::is_permutation_inner ( first1, last1, first2, last2, p ); | |
124 | } | |
125 | ||
126 | return true; | |
127 | } | |
128 | ||
129 | /// \fn is_permutation ( ForwardIterator1 first, ForwardIterator1 last, ForwardIterator2 first2 ) | |
130 | /// \brief Tests to see if the sequence [first,last) is a permutation of the sequence starting at first2 | |
131 | /// | |
132 | /// \param first1 The start of the input sequence | |
133 | /// \param last2 One past the end of the input sequence | |
134 | /// \param first2 The start of the second sequence | |
135 | /// \note This function is part of the C++2011 standard library. | |
136 | template< class ForwardIterator1, class ForwardIterator2 > | |
137 | bool is_permutation ( ForwardIterator1 first1, ForwardIterator1 last1, ForwardIterator2 first2 ) | |
138 | { | |
139 | // How should I deal with the idea that ForwardIterator1::value_type | |
140 | // and ForwardIterator2::value_type could be different? Define my own comparison predicate? | |
141 | // Skip the common prefix (if any) | |
142 | std::pair<ForwardIterator1, ForwardIterator2> eq = std::mismatch (first1, last1, first2 ); | |
143 | first1 = eq.first; | |
144 | first2 = eq.second; | |
145 | if ( first1 != last1 ) { | |
146 | // Create last2 | |
147 | ForwardIterator2 last2 = first2; | |
148 | std::advance ( last2, std::distance (first1, last1)); | |
149 | return boost::algorithm::detail::is_permutation_inner ( first1, last1, first2, last2, | |
150 | std::equal_to<typename std::iterator_traits<ForwardIterator1>::value_type> ()); | |
151 | } | |
152 | return true; | |
153 | } | |
154 | ||
155 | ||
156 | /// \fn is_permutation ( const Range &r, ForwardIterator first2 ) | |
157 | /// \brief Tests to see if the sequence [first,last) is a permutation of the sequence starting at first2 | |
158 | /// | |
159 | /// \param r The input range | |
160 | /// \param first2 The start of the second sequence | |
161 | template <typename Range, typename ForwardIterator> | |
162 | bool is_permutation ( const Range &r, ForwardIterator first2 ) | |
163 | { | |
164 | return boost::algorithm::is_permutation (boost::begin (r), boost::end (r), first2 ); | |
165 | } | |
166 | ||
167 | /// \fn is_permutation ( const Range &r, ForwardIterator first2, BinaryPredicate pred ) | |
168 | /// \brief Tests to see if the sequence [first,last) is a permutation of the sequence starting at first2 | |
169 | /// | |
170 | /// \param r The input range | |
171 | /// \param first2 The start of the second sequence | |
172 | /// \param pred The predicate to compare elements with | |
173 | /// | |
174 | // Disable this template when the first two parameters are the same type | |
175 | // That way the non-range version will be chosen. | |
176 | template <typename Range, typename ForwardIterator, typename BinaryPredicate> | |
177 | typename boost::disable_if_c<boost::is_same<Range, ForwardIterator>::value, bool>::type | |
178 | is_permutation ( const Range &r, ForwardIterator first2, BinaryPredicate pred ) | |
179 | { | |
180 | return boost::algorithm::is_permutation (boost::begin (r), boost::end (r), first2, pred ); | |
181 | } | |
182 | ||
183 | }} | |
184 | ||
185 | #endif // BOOST_ALGORITHM_IS_PERMUTATION11_HPP |