1 /*
2 Copyright (c) Alexander Zaitsev <zamazan4ik@gmail.com>, 2016
3
4 Distributed under the Boost Software License, Version 1.0. (See
5 accompanying file LICENSE_1_0.txt or copy at
6 http://www.boost.org/LICENSE_1_0.txt)
7
8 See http://www.boost.org/ for latest version.
9 */
10
11 /// \file is_palindrome.hpp
12 /// \brief Checks the input sequence on palindrome.
13 /// \author Alexander Zaitsev
14
15 #ifndef BOOST_ALGORITHM_IS_PALINDROME_HPP
16 #define BOOST_ALGORITHM_IS_PALINDROME_HPP
17
18 #include <iterator>
19 #include <functional>
20 #include <cstring>
21
22 #include <boost/config.hpp>
23 #include <boost/range/begin.hpp>
24 #include <boost/range/end.hpp>
25
26 namespace boost { namespace algorithm {
27
28 /// \fn is_palindrome ( BidirectionalIterator begin, BidirectionalIterator end, Predicate p )
29 /// \return true if the entire sequence is palindrome
30 ///
31 /// \param begin The start of the input sequence
32 /// \param end One past the end of the input sequence
33 /// \param p A predicate used to compare the values.
34 ///
35 /// \note This function will return true for empty sequences and for palindromes.
36 /// For other sequences function will return false.
37 /// Complexity: O(N).
38 template <typename BidirectionalIterator, typename Predicate>
is_palindrome(BidirectionalIterator begin,BidirectionalIterator end,Predicate p)39 bool is_palindrome(BidirectionalIterator begin, BidirectionalIterator end, Predicate p)
40 {
41 if(begin == end)
42 {
43 return true;
44 }
45
46 --end;
47 while(begin != end)
48 {
49 if(!p(*begin, *end))
50 {
51 return false;
52 }
53 ++begin;
54 if(begin == end)
55 {
56 break;
57 }
58 --end;
59 }
60 return true;
61 }
62
63 /// \fn is_palindrome ( BidirectionalIterator begin, BidirectionalIterator end )
64 /// \return true if the entire sequence is palindrome
65 ///
66 /// \param begin The start of the input sequence
67 /// \param end One past the end of the input sequence
68 ///
69 /// \note This function will return true for empty sequences and for palindromes.
70 /// For other sequences function will return false.
71 /// Complexity: O(N).
72 template <typename BidirectionalIterator>
is_palindrome(BidirectionalIterator begin,BidirectionalIterator end)73 bool is_palindrome(BidirectionalIterator begin, BidirectionalIterator end)
74 {
75 return is_palindrome(begin, end,
76 std::equal_to<typename std::iterator_traits<BidirectionalIterator>::value_type> ());
77 }
78
79 /// \fn is_palindrome ( const R& range )
80 /// \return true if the entire sequence is palindrome
81 ///
82 /// \param range The range to be tested.
83 ///
84 /// \note This function will return true for empty sequences and for palindromes.
85 /// For other sequences function will return false.
86 /// Complexity: O(N).
87 template <typename R>
is_palindrome(const R & range)88 bool is_palindrome(const R& range)
89 {
90 return is_palindrome(boost::begin(range), boost::end(range));
91 }
92
93 /// \fn is_palindrome ( const R& range, Predicate p )
94 /// \return true if the entire sequence is palindrome
95 ///
96 /// \param range The range to be tested.
97 /// \param p A predicate used to compare the values.
98 ///
99 /// \note This function will return true for empty sequences and for palindromes.
100 /// For other sequences function will return false.
101 /// Complexity: O(N).
102 template <typename R, typename Predicate>
is_palindrome(const R & range,Predicate p)103 bool is_palindrome(const R& range, Predicate p)
104 {
105 return is_palindrome(boost::begin(range), boost::end(range), p);
106 }
107
108 /// \fn is_palindrome ( const char* str )
109 /// \return true if the entire sequence is palindrome
110 ///
111 /// \param str C-string to be tested.
112 ///
113 /// \note This function will return true for empty sequences and for palindromes.
114 /// For other sequences function will return false.
115 /// Complexity: O(N).
is_palindrome(const char * str)116 bool is_palindrome(const char* str)
117 {
118 if(!str)
119 return true;
120 return is_palindrome(str, str + strlen(str));
121 }
122
123 /// \fn is_palindrome ( const char* str, Predicate p )
124 /// \return true if the entire sequence is palindrome
125 ///
126 /// \param str C-string to be tested.
127 /// \param p A predicate used to compare the values.
128 ///
129 /// \note This function will return true for empty sequences and for palindromes.
130 /// For other sequences function will return false.
131 /// Complexity: O(N).
132 template<typename Predicate>
is_palindrome(const char * str,Predicate p)133 bool is_palindrome(const char* str, Predicate p)
134 {
135 if(!str)
136 return true;
137 return is_palindrome(str, str + strlen(str), p);
138 }
139 }}
140
141 #endif // BOOST_ALGORITHM_IS_PALINDROME_HPP
142