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<H2>set_intersection()</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>A basic set operation (algorithm) for constructing a sorted intersection</P>
<A NAME="sec3"><H3>Synopsis</H3></A>

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

namespace std {
  template &lt;class InputIterator1, class InputIterator2, 
            class OutputIterator&gt;
  OutputIterator  
  set_intersection(InputIterator1 start1, 
                   InputIterator1 finish1,
                   InputIterator2 start2, 
                   InputIterator2 finish2,
                   OutputIterator result);
  template &lt;class InputIterator1, class InputIterator2, 
            class OutputIterator, class Compare&gt;
  OutputIterator  
  set_intersection(InputIterator1 start1, 
                   InputIterator1 finish1,
                   InputIterator2 start2, 
                   InputIterator2 finish2, 
                   OutputIterator result, 
                   Compare comp);
}
</PRE>
<A NAME="sec4"><H3>Description</H3></A>
<P>The <SAMP>set_intersection()</SAMP> algorithm constructs a sorted intersection of elements from the two ranges. It returns the end of the constructed range. When it finds an element present in both ranges, <SAMP>set_intersection()</SAMP> always copies the element from the first range into <SAMP>result</SAMP>. This means that the result of <SAMP>set_intersection()</SAMP> is guaranteed to be stable.   The result of <SAMP>set_intersection()</SAMP> is undefined if the result range overlaps with either of the original ranges. </P>
<P><SAMP>set_intersection()</SAMP> assumes that the ranges are sorted using <SAMP>operator&lt;()</SAMP>, unless an alternative comparison function object (<SAMP>comp</SAMP>) is provided. </P>
<A NAME="sec5"><H3>Complexity</H3></A>
<P>At most <SAMP>((finish1 - start1) + (finish2 - start2)) * 2 -1</SAMP> comparisons are performed.</P>
<A NAME="sec6"><H3>Example</H3></A>

<UL><PRE>//
//  set_intr.cpp
//

#include &lt;algorithm&gt;
#include &lt;set&gt;
#include &lt;iostream&gt;

int main ()
{
#ifndef _RWSTD_NO_NAMESPACE
  using namespace std;
#endif


  // Initialize some sets.

  int a1[10] = {1,3,5,7,9,11};
  int a3[4]  = {3,5,7,8};
  set&lt;int, less&lt;int&gt;,allocator&lt;int&gt;  &gt; odd(a1+0, a1+6),
                                       result, 
                                       smalll(a3+0, a3+4);

  // Create an insert_iterator for result.

  insert_iterator&lt;set&lt;int, less&lt;int&gt;,allocator&lt;int&gt; &gt; &gt; 
                  res_ins(result, result.begin());

  // Demonstrate set_intersection.

  cout &lt;&lt; "The result of:" &lt;&lt; endl &lt;&lt; "{";
  copy(smalll.begin(),smalll.end(), 
       ostream_iterator&lt;int,char,char_traits&lt;char&gt; &gt;
                       (cout," "));
  cout &lt;&lt; "} intersection {";
  copy(odd.begin(),odd.end(),
       ostream_iterator&lt;int,char,char_traits&lt;char&gt; &gt;
                       (cout," "));
  cout &lt;&lt; "} =" &lt;&lt; endl &lt;&lt; "{";

  set_intersection(smalll.begin(),smalll.end(),
                   odd.begin(),odd.end(),res_ins);
  copy(result.begin(),result.end(),
       ostream_iterator&lt;int,char,char_traits&lt;char&gt; &gt;
                       (cout," "));
  cout &lt;&lt; "}" &lt;&lt; endl &lt;&lt; endl;

  return 0;
}


Program Output:
</PRE></UL>
<UL><PRE>The result of:
{3 5 7 8 } intersection {1 3 5 7 9 11 } =
{3 5 7 }

</PRE></UL>
<A NAME="sec7"><H3>See Also</H3></A>
<P><SAMP><A HREF="includes.html">includes()</A></SAMP>, <A HREF="iterators.html">Iterators</A>, <SAMP><A HREF="set-union.html">set_union()</A></SAMP>, <SAMP><A HREF="set-difference.html">set_difference()</A></SAMP>, <SAMP><A HREF="set-symmetric-difference.html">set_symmetric_difference()</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++, 25.3.5.3</I></P>

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