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<P>©Copyright 1996 Rogue Wave Software</P>
<H2>reverse</H2>
<HR><PRE> Algorithm</PRE><HR>
<A NAME="Summary"><H3>Summary</H3></A>
<P>Reverse the order of elements in a collection.</P>
<H3>Contents</H3>
<UL>
<A HREF="#Synopsis"><LI>Synopsis</LI></A>
<A HREF="#Description"><LI>Description</LI></A>
<A HREF="#Complexity"><LI>Complexity</LI></A>
<A HREF="#Example"><LI>Example</LI></A>
<A HREF="#Warning"><LI>Warning</LI></A>
<A HREF="#See Also"><LI>See Also</LI></A>
</UL>
<A NAME="Synopsis"><H3>Synopsis</H3></A>
<PRE>#include <algorithm></PRE>
<PRE>
template <class BidirectionalIterator>
void <B>reverse</B> (BidirectionalIterator first,
BidirectionalIterator last);</PRE>
<A NAME="Description"><H3>Description</H3></A>
<P>The algorithm <B><I>reverse</B></I> 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 <= (last - first)/2</SAMP> , <B><I>reverse</B></I> applies <A HREF="swa_4514.htm"><B><I>swap</B></I></A> to all pairs of iterators <SAMP>first + I, (last - I) - 1</SAMP>. </P>
<P>Because the iterators are assumed to be bidirectional, <B><I>reverse</B></I> does not return anything.</P>
<A NAME="Complexity"><H3>Complexity</H3></A>
<P><B><I>reverse</B></I> performs exactly <SAMP>(last - first)/2</SAMP> swaps.</P>
<A NAME="Example"><H3>Example</H3></A>
<PRE>//
// reverse.cpp
//
#include <algorithm>
#include <vector>
#include <iostream.h>
int main()
{
//Initialize a vector with an array of ints
int arr[10] = {1,2,3,4,5,6,7,8,9,10};
vector<int> v(arr, arr+10);
//Print out elements in original (sorted) order
cout << "Elements before reverse: " << endl << " ";
copy(v.begin(),v.end(),ostream_iterator<int>(cout," "));
cout << endl << endl;
//Reverse the ordering
<B>reverse</B>(v.begin(), v.end());
//Print out the reversed elements
cout << "Elements after reverse: " << endl << " ";
copy(v.begin(),v.end(),ostream_iterator<int>(cout," "));
cout << endl;
return 0;
}
Output :
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>
<A NAME="Warning"><H3>Warning</H3></A>
<P>If your compiler does not support default template parameters, then you need to always supply the <SAMP>Allocator</SAMP> template argument. For instance, you will need to write :</P>
<P><SAMP>vector<int, allocator></SAMP></P>
<P>instead of :</P>
<P><SAMP>vector<int></SAMP></P>
<A NAME="See Also"><H3>See Also</H3></A>
<P><A HREF="rev_6851.htm"><B><I>reverse_copy</B></I></A>, <A HREF="swa_4514.htm"><B><I>swap</B></I></A></P>
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