forked from boostorg/algorithm
131 lines
4.4 KiB
Plaintext
131 lines
4.4 KiB
Plaintext
[/ QuickBook Document version 1.5 ]
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[section:is_sorted is_sorted ]
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[/license
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Copyright (c) 2010-2012 Marshall Clow
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Distributed under the Boost Software License, Version 1.0.
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(See accompanying file LICENSE_1_0.txt or copy at
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http://www.boost.org/LICENSE_1_0.txt)
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]
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The header file `<boost/algorithm/cxx11/is_sorted.hpp>` contains functions for determining if a sequence is ordered.
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[heading is_sorted]
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The function `is_sorted(sequence)` determines whether or not a sequence is completely sorted according so some criteria. If no comparison predicate is specified, then std::less_equal is used (i.e, the test is to see if the sequence is non-decreasing)
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``
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namespace boost { namespace algorithm {
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template <typename Iterator, typename Pred>
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bool is_sorted ( Iterator first, Iterator last, Pred p );
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template <typename Iterator>
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bool is_sorted ( Iterator first, Iterator last );
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template <typename Range, typename Pred>
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bool is_sorted ( const Range &r, Pred p );
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template <typename Range>
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bool is_sorted ( const Range &r );
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}}
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``
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Iterator requirements: The `is_sorted` functions will work on all kinds of iterators (except output iterators).
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[heading is_sorted_until]
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If `distance(first, last) < 2`, then `is_sorted ( first, last )` returns `last`. Otherwise, it returns the last iterator i in [first,last] for which the range [first,i) is sorted.
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In short, it returns the element in the sequence that is "out of order". If the entire sequence is sorted (according to the predicate), then it will return `last`.
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``
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namespace boost { namespace algorithm {
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template <typename ForwardIterator, typename Pred>
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FI is_sorted_until ( ForwardIterator first, ForwardIterator last, Pred p );
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template <typename ForwardIterator>
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ForwardIterator is_sorted_until ( ForwardIterator first, ForwardIterator last );
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template <typename Range, typename Pred>
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typename boost::range_iterator<const R>::type is_sorted_until ( const Range &r, Pred p );
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template <typename Range>
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typename boost::range_iterator<const R>::type is_sorted_until ( const Range &r );
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}}
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``
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Iterator requirements: The `is_sorted_until` functions will work on forward iterators or better. Since they have to return a place in the input sequence, input iterators will not suffice.
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Complexity:
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`is_sorted_until` will make at most ['N-1] calls to the predicate (given a sequence of length ['N]).
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Examples:
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Given the sequence `{ 1, 2, 3, 4, 5, 3 }`, `is_sorted_until ( beg, end, std::less<int>())` would return an iterator pointing at the second `3`.
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Given the sequence `{ 1, 2, 3, 4, 5, 9 }`, `is_sorted_until ( beg, end, std::less<int>())` would return `end`.
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There are also a set of "wrapper functions" for is_ordered which make it easy to see if an entire sequence is ordered. These functions return a boolean indicating success or failure rather than an iterator to where the out of order items were found.
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To test if a sequence is increasing (each element at least as large as the preceding one):
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``
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namespace boost { namespace algorithm {
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template <typename Iterator>
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bool is_increasing ( Iterator first, Iterator last );
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template <typename R>
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bool is_increasing ( const R &range );
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}}
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``
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To test if a sequence is decreasing (each element no larger than the preceding one):
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``
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namespace boost { namespace algorithm {
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template <typename Iterator>
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bool is_decreasing ( Iterator first, Iterator last );
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template <typename R>
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bool is_decreasing ( const R &range );
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}}
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``
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To test if a sequence is strictly increasing (each element larger than the preceding one):
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``
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namespace boost { namespace algorithm {
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template <typename Iterator>
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bool is_strictly_increasing ( Iterator first, Iterator last );
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template <typename R>
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bool is_strictly_increasing ( const R &range );
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}}
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``
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To test if a sequence is strictly decreasing (each element smaller than the preceding one):
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``
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namespace boost { namespace algorithm {
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template <typename Iterator>
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bool is_strictly_decreasing ( Iterator first, Iterator last );
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template <typename R>
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bool is_strictly_decreasing ( const R &range );
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}}
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``
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Complexity:
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Each of these calls is just a thin wrapper over `is_sorted`, so they have the same complexity as `is_sorted`.
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[heading Notes]
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* The routines `is_sorted` and `is_sorted_until` are part of the C++11 standard. When compiled using a C++11 implementation, the implementation from the standard library will be used.
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* `is_sorted` and `is_sorted_until` both return true for empty ranges and ranges of length one.
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[endsect]
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