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| <TITLE>set_difference()</TITLE> |
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| <H2>set_difference()</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 difference</P> |
| <A NAME="sec3"><H3>Synopsis</H3></A> |
| |
| <PRE>#include <algorithm> |
| |
| namespace std { |
| template <class InputIterator1, class InputIterator2, |
| class OutputIterator> |
| OutputIterator |
| set_difference(InputIterator1 start1, |
| InputIterator1 finish1, |
| InputIterator2 start2, |
| InputIterator2 finish2, |
| OutputIterator result); |
| template <class InputIterator1, class InputIterator2, |
| class OutputIterator, class Compare> |
| OutputIterator |
| set_difference(InputIterator1 start1, |
| InputIterator1 finish1, |
| InputIterator2 start2, |
| InputIterator2 finish2, |
| OutputIterator result, |
| Compare comp); |
| } |
| </PRE> |
| <A NAME="sec4"><H3>Description</H3></A> |
| <P>The <SAMP>set_difference()</SAMP> algorithm constructs a sorted difference that includes copies of the elements that are present in the range <SAMP>[start1, finish1)</SAMP> but are not present in the range <SAMP>[start2, finish2)</SAMP>. It returns the end of the constructed range. </P> |
| <P>As an example, assume we have the following two sets:</P> |
| <P><SAMP>1 2 3 4 5</SAMP></P> |
| <P>and </P> |
| <P><SAMP>3 4 5 6 7</SAMP></P> |
| <P>The result of applying <SAMP>set_difference()</SAMP> is the set:</P> |
| <P><SAMP>1 2</SAMP></P> |
| <P>The result of <SAMP>set_difference()</SAMP> is undefined if the result range overlaps with either of the original ranges. </P> |
| <P><SAMP>set_difference()</SAMP> assumes that the ranges are sorted using <SAMP>operator<()</SAMP>, unless an alternative comparison function object (<SAMP>comp</SAMP>) is provided. </P> |
| <P>Use the <SAMP>set_symetric_difference()</SAMP> algorithm to obtain a result that contains all elements that are not in common between the two sets.</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_diff.cpp |
| // |
| |
| #include <algorithm> |
| #include <set> |
| #include <iostream> |
| |
| int main () |
| { |
| #ifndef _RWSTD_NO_NAMESPACE |
| using namespace std; |
| #endif |
| |
| |
| // Initialize some sets. |
| |
| int a1[10] = {1,2,3,4,5,6,7,8,9,10}; |
| int a2[6] = {2,4,6,8,10,12}; |
| |
| set<int, less<int>,allocator<int> > all(a1+0, a1+10), |
| even(a2+0, a2+6), odd; |
| |
| // Create an insert_iterator for odd. |
| |
| insert_iterator<set <int, less<int>,allocator<int> > > |
| odd_ins(odd, odd.begin()); |
| |
| // Demonstrate set_difference. |
| |
| cout << "The result of:" << endl << "{"; |
| copy(all.begin(),all.end(), |
| ostream_iterator<int,char,char_traits<char> > |
| (cout," ")); |
| cout << "} - {"; |
| copy(even.begin(),even.end(), |
| ostream_iterator<int,char,char_traits<char> > |
| (cout," ")); |
| cout << "} =" << endl << "{"; |
| set_difference(all.begin(), all.end(), even.begin(), |
| even.end(), odd_ins); |
| copy(odd.begin(),odd.end(), |
| ostream_iterator<int,char,char_traits<char> > |
| (cout," ")); |
| cout << "}" << endl << endl; |
| |
| return 0; |
| } |
| |
| |
| Program Output: |
| </PRE></UL> |
| <UL><PRE>The result of: |
| {1 2 3 4 5 6 7 8 9 10 } - {2 4 6 8 10 12 } = |
| {1 3 5 7 9 } |
| |
| </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-intersection.html">set_intersection()</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 25.3.5.4</I></P> |
| |
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