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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/range/begin.hpp>
23#include <boost/range/end.hpp>
24
25namespace boost { namespace algorithm {
26
27/// \fn is_palindrome ( BidirectionalIterator begin, BidirectionalIterator end, Predicate p )
28/// \return true if the entire sequence is palindrome
29///
30/// \param begin The start of the input sequence
31/// \param end One past the end of the input sequence
32/// \param p A predicate used to compare the values.
33///
34/// \note This function will return true for empty sequences and for palindromes.
35/// For other sequences function will return false.
36/// Complexity: O(N).
37template <typename BidirectionalIterator, typename Predicate>
38bool is_palindrome(BidirectionalIterator begin, BidirectionalIterator end, Predicate p )
39{
40 if(begin == end)
41 {
42 return true;
43 }
44
45 --end;
46 while(begin != end)
47 {
48 if(!p(*begin, *end))
49 {
50 return false;
51 }
52 ++begin;
53 if(begin == end)
54 {
55 break;
56 }
57 --end;
58 }
59 return true;
60}
61
62/// \fn is_palindrome ( BidirectionalIterator begin, BidirectionalIterator end )
63/// \return true if the entire sequence is palindrome
64///
65/// \param begin The start of the input sequence
66/// \param end One past the end of the input sequence
67///
68/// \note This function will return true for empty sequences and for palindromes.
69/// For other sequences function will return false.
70/// Complexity: O(N).
71template <typename BidirectionalIterator>
72bool is_palindrome(BidirectionalIterator begin, BidirectionalIterator end)
73{
74 if(begin == end)
75 {
76 return true;
77 }
78
79 --end;
80 while(begin != end)
81 {
82 if(!(*begin == *end))
83 {
84 return false;
85 }
86 ++begin;
87 if(begin == end)
88 {
89 break;
90 }
91 --end;
92 }
93 return true;
94}
95
96/// \fn is_palindrome ( const R& range )
97/// \return true if the entire sequence is palindrome
98///
99/// \param range The range to be tested.
100///
101/// \note This function will return true for empty sequences and for palindromes.
102/// For other sequences function will return false.
103/// Complexity: O(N).
104template <typename R>
105bool is_palindrome(const R& range)
106{
107 return is_palindrome(boost::begin(range), boost::end(range));
108}
109
110/// \fn is_palindrome ( const R& range, Predicate p )
111/// \return true if the entire sequence is palindrome
112///
113/// \param range The range to be tested.
114/// \param p A predicate used to compare the values.
115///
116/// \note This function will return true for empty sequences and for palindromes.
117/// For other sequences function will return false.
118/// Complexity: O(N).
119template <typename R, typename Predicate>
120bool is_palindrome(const R& range, Predicate p)
121{
122 return is_palindrome(boost::begin(range), boost::end(range), p);
123}
124
125
126/// \fn is_palindrome ( const char* str )
127/// \return true if the entire sequence is palindrome
128///
129/// \param str C-string to be tested.
130///
131/// \note This function will return true for empty sequences and for palindromes.
132/// For other sequences function will return false.
133/// Complexity: O(N).
134bool is_palindrome(const char* str)
135{
136 if(!str)
137 return true;
138 return is_palindrome(str, str + strlen(str));
139}
140
141
142/// \fn is_palindrome ( const char* str, Predicate p )
143/// \return true if the entire sequence is palindrome
144///
145/// \param str C-string to be tested.
146/// \param p A predicate used to compare the values.
147///
148/// \note This function will return true for empty sequences and for palindromes.
149/// For other sequences function will return false.
150/// Complexity: O(N).
151template<typename Predicate>
152bool is_palindrome(const char* str, Predicate p)
153{
154 if(!str)
155 return true;
156 return is_palindrome(str, str + strlen(str), p);
157}
158
159}}
160
161#endif // BOOST_ALGORITHM_IS_PALINDROME_HPP