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149 lines
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<HTML>
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<HEAD>
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<TITLE>set_union()</TITLE>
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<LINK REL=StyleSheet HREF="../rw.css" TYPE="text/css" TITLE="Apache stdcxx Stylesheet"></HEAD>
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<A HREF="set-symmetric-difference.html"><IMG SRC="images/bprev.gif" WIDTH=20 HEIGHT=21 ALT="Previous file" BORDER=O></A><A HREF="noframes.html"><IMG SRC="images/btop.gif" WIDTH=56 HEIGHT=21 ALT="Top of Document" BORDER=O></A><A HREF="booktoc.html"><IMG SRC="images/btoc.gif" WIDTH=56 HEIGHT=21 ALT="Contents" BORDER=O></A><A HREF="tindex.html"><IMG SRC="images/bindex.gif" WIDTH=56 HEIGHT=21 ALT="Index page" BORDER=O></A><A HREF="slice.html"><IMG SRC="images/bnext.gif" WIDTH=25 HEIGHT=21 ALT="Next file" BORDER=O></A><DIV CLASS="DOCUMENTNAME"><B>Apache C++ Standard Library Reference Guide</B></DIV>
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<H2>set_union()</H2>
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<P><B>Library:</B> <A HREF="2-9.html">Algorithms</A></P>
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<PRE><HR><B><I>Function</I></B><HR></PRE>
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<UL>
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<LI><A HREF="#sec1">Local Index</A></LI>
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<LI><A HREF="#sec2">Summary</A></LI>
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<LI><A HREF="#sec3">Synopsis</A></LI>
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<LI><A HREF="#sec4">Description</A></LI>
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<LI><A HREF="#sec5">Complexity</A></LI>
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<LI><A HREF="#sec6">Example</A></LI>
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<LI><A HREF="#sec7">See Also</A></LI>
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<LI><A HREF="#sec8">Standards Conformance</A></LI>
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</UL>
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<A NAME="sec1"><H3>Local Index</H3></A>
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No Entries
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<A NAME="sec2"><H3>Summary</H3></A>
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<P>A basic set operation (algorithm) for constructing a sorted union</P>
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<A NAME="sec3"><H3>Synopsis</H3></A>
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<PRE>#include <algorithm>
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namespace std {
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template <class InputIterator1, class InputIterator2,
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class OutputIterator>
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OutputIterator
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set_union(InputIterator1 start1, InputIterator1 finish1,
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InputIterator2 start2, InputIterator2 finish2,
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OutputIterator result);
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template <class InputIterator1, class InputIterator2,
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class OutputIterator, class Compare>
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OutputIterator
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set_union(InputIterator1 start1, InputIterator1 finish1,
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InputIterator2 start2, InputIterator2 finish2,
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OutputIterator result, Compare comp);
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}
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</PRE>
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<A NAME="sec4"><H3>Description</H3></A>
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<P>The <SAMP>set_union()</SAMP> algorithm constructs a sorted union of the elements from the two ranges. It returns the end of the constructed range. <SAMP>set_union()</SAMP> is stable, which means that if an element is present in both ranges, the one from the first range is copied. The result of <SAMP>set_union()</SAMP> is undefined if the result range overlaps with either of the original ranges. Note that <SAMP>set_union()</SAMP> does not merge the two sorted sequences. If an element is present in both sequences, only the element from the first sequence is copied to <SAMP>result</SAMP>. (Use the <SAMP><A HREF="merge.html">merge()</A></SAMP> algorithm to create an ordered merge of two sorted sequences that contains all the elements from both sequences.)</P>
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<P><SAMP>set_union()</SAMP> assumes that the sequences are sorted using <SAMP>operator<()</SAMP>, unless an alternative comparison function object (<SAMP>comp</SAMP>) is provided. </P>
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<A NAME="sec5"><H3>Complexity</H3></A>
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<P>At most <SAMP>((finish1 - start1) + (finish2 - start2)) * 2 -1</SAMP> comparisons are performed.</P>
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<A NAME="sec6"><H3>Example</H3></A>
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<UL><PRE>//
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// set_unin.cpp
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//
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#include <algorithm>
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#include <set>
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#include <iostream>
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int main ()
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{
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_USING (namespace std);
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typedef set<int, less<int>,allocator<int> > Set;
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// Initialize sets.
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int a1[] = {2, 4, 6, 8, 10, 12};
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int a2[] = {3, 5, 7, 8};
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Set s1 (a1, a1 + sizeof a1 / sizeof *a1);
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Set s2 (a2, a2 + sizeof a2 / sizeof *a2);
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Set result;
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// Create an insert_iterator for result.
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insert_iterator<Set> res_ins (result, result.begin ());
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// Compute union of two sets.
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set_union (s2.begin (), s2.end (),
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s1.begin (), s1.end (), res_ins);
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// Display result on standard output.
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typedef ostream_iterator<int, char, char_traits<char> >
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OSIter;
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cout << "The result of:" << endl << "{ ";
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copy (s2.begin (),s2.end (), OSIter (cout," "));
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cout << "} union { ";
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copy (s1.begin (),s1.end (), OSIter (cout," "));
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cout << "} =" << endl << "{ ";
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copy (result.begin (),result.end (), OSIter (cout," "));
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cout << "}" << endl << endl;
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return 0;
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}
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Program Output:
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</PRE></UL>
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<UL><PRE>The result of:
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{ 3 5 7 8 } union { 2 4 6 8 10 12 } =
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{ 2 3 4 5 6 7 8 10 12 }
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</PRE></UL>
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<A NAME="sec7"><H3>See Also</H3></A>
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<P><SAMP><A HREF="includes.html">includes()</A></SAMP>, <A HREF="iterators.html">Iterators</A>, <SAMP><A HREF="set-intersection.html">set_intersection()</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>
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<A NAME="sec8"><H3>Standards Conformance</H3></A>
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<P><I>ISO/IEC 14882:1998 -- International Standard for Information Systems -- Programming Language C++, Section 25.3.5.2</I></P>
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