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<H2>reverse()</H2>
<P><B>Library:</B>&nbsp;&nbsp;<A HREF="2-9.html">Algorithms</A></P>

<PRE><HR><B><I>Function</I></B><HR></PRE>

<UL>
<LI><A HREF="#sec1">Local Index</A></LI>
<LI><A HREF="#sec2">Summary</A></LI>
<LI><A HREF="#sec3">Synopsis</A></LI>
<LI><A HREF="#sec4">Description</A></LI>
<LI><A HREF="#sec5">Complexity</A></LI>
<LI><A HREF="#sec6">Example</A></LI>
<LI><A HREF="#sec7">See Also</A></LI>
<LI><A HREF="#sec8">Standards Conformance</A></LI>
</UL>
<A NAME="sec1"><H3>Local Index</H3></A>
No Entries
<A NAME="sec2"><H3>Summary</H3></A>
<P>An algorithm that reverses the order of elements in a sequence</P>
<A NAME="sec3"><H3>Synopsis</H3></A>

<PRE>#include &lt;algorithm&gt;

namespace std {
  template &lt;class BidirectionalIterator&gt;
  void reverse(BidirectionalIterator start,
               BidirectionalIterator finish);
}
</PRE>
<A NAME="sec4"><H3>Description</H3></A>
<P>The algorithm <SAMP>reverse()</SAMP> reverses the elements in a sequence so that the last element becomes the new first element, and the first element becomes the new last. For each non-negative integer <SAMP>i &lt;= (finish - start)/2</SAMP>, <SAMP>reverse()</SAMP> applies <SAMP><A HREF="iter-swap.html">iter_swap()</A></SAMP> to all pairs of iterators <SAMP>start + I, (finish&nbsp;-&nbsp;I)&nbsp;- 1</SAMP>. </P>
<A NAME="sec5"><H3>Complexity</H3></A>
<P><SAMP>reverse()</SAMP> performs exactly <SAMP>(finish - start)/2</SAMP> swaps.</P>
<A NAME="sec6"><H3>Example</H3></A>

<UL><PRE>//
//  reverse.cpp
//

#include &lt;algorithm&gt;   // for reverse, reverse_copy
#include &lt;vector&gt;      // for vector
#include &lt;iostream&gt;    // for cout, endl
#include &lt;iterator&gt;    // for ostream_iterator


int main ()
{
    typedef std::vector&lt;int, std::allocator&lt;int&gt; &gt; Vector;
    typedef std::ostream_iterator&lt;int, char,
                                  std::char_traits&lt;char&gt; &gt;
            Iter;

    // Initialize a vector with an array of integers.
    const Vector::value_type a[] = { 1, 2, 3, 4, 5, 
                                     6, 7, 8, 9, 10 };

    Vector v (a + 0, a + sizeof a / sizeof *a);

    // Print out elements in original (sorted) order.
    std::cout &lt;&lt; "Elements before reverse: \n     ";
    std::copy (v.begin (), v.end (), Iter (std::cout, " "));

    // Reverse the ordering.
    std::reverse (v.begin (), v.end ());

    // Print out the reversed elements.
    std::cout &lt;&lt; "\n\nElements after reverse: \n     ";
    std::copy (v.begin (), v.end (), Iter (std::cout, " "));

    std::cout &lt;&lt; "\n\nA reverse_copy to cout: \n     ";
    std::reverse_copy (v.begin (), v.end (), 
                       Iter (std::cout, " "));
    std::cout &lt;&lt; std::endl;

    return 0;
}


Program Output:
</PRE></UL>
<UL><PRE>Elements before reverse: 
     1 2 3 4 5 6 7 8 9 10 

Elements after reverse: 
     10 9 8 7 6 5 4 3 2 1 

A reverse_copy to cout: 
     1 2 3 4 5 6 7 8 9 10 
</PRE></UL>
<A NAME="sec7"><H3>See Also</H3></A>
<P><SAMP><A HREF="reverse-copy.html">reverse_copy()</A></SAMP>, <SAMP><A HREF="swap.html">swap()</A></SAMP></P>
<A NAME="sec8"><H3>Standards Conformance</H3></A>
<P><I>ISO/IEC 14882:1998 -- International Standard for Information Systems -- Programming Language C++, Section 25.2.9</I></P>

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