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| <TITLE>set_union()</TITLE> |
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| <H2>set_union()</H2> |
| <P><B>Library:</B> <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 union</P> |
| <A NAME="sec3"><H3>Synopsis</H3></A> |
| |
| <PRE>#include <algorithm> |
| |
| namespace std { |
| template <class InputIterator1, class InputIterator2, |
| class OutputIterator> |
| OutputIterator |
| set_union(InputIterator1 start1, InputIterator1 finish1, |
| InputIterator2 start2, InputIterator2 finish2, |
| OutputIterator result); |
| |
| template <class InputIterator1, class InputIterator2, |
| class OutputIterator, class Compare> |
| OutputIterator |
| set_union(InputIterator1 start1, InputIterator1 finish1, |
| InputIterator2 start2, InputIterator2 finish2, |
| OutputIterator result, Compare comp); |
| } |
| </PRE> |
| <A NAME="sec4"><H3>Description</H3></A> |
| <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> |
| <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> |
| <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_unin.cpp |
| // |
| |
| #include <algorithm> |
| #include <set> |
| #include <iostream> |
| |
| int main () |
| { |
| _USING (namespace std); |
| |
| typedef set<int, less<int>,allocator<int> > Set; |
| |
| // Initialize sets. |
| |
| int a1[] = {2, 4, 6, 8, 10, 12}; |
| int a2[] = {3, 5, 7, 8}; |
| |
| Set s1 (a1, a1 + sizeof a1 / sizeof *a1); |
| Set s2 (a2, a2 + sizeof a2 / sizeof *a2); |
| Set result; |
| |
| // Create an insert_iterator for result. |
| |
| insert_iterator<Set> res_ins (result, result.begin ()); |
| |
| // Compute union of two sets. |
| |
| set_union (s2.begin (), s2.end (), |
| s1.begin (), s1.end (), res_ins); |
| |
| // Display result on standard output. |
| |
| typedef ostream_iterator<int, char, char_traits<char> > |
| OSIter; |
| |
| cout << "The result of:" << endl << "{ "; |
| copy (s2.begin (),s2.end (), OSIter (cout," ")); |
| cout << "} union { "; |
| copy (s1.begin (),s1.end (), OSIter (cout," ")); |
| cout << "} =" << endl << "{ "; |
| copy (result.begin (),result.end (), OSIter (cout," ")); |
| cout << "}" << endl << endl; |
| |
| return 0; |
| } |
| |
| |
| Program Output: |
| </PRE></UL> |
| <UL><PRE>The result of: |
| { 3 5 7 8 } union { 2 4 6 8 10 12 } = |
| { 2 3 4 5 6 7 8 10 12 } |
| |
| </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-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> |
| <A NAME="sec8"><H3>Standards Conformance</H3></A> |
| <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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