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It is provided "as is" without express or implied warranty. -- --><Head><Title>set_symmetric_difference</Title><!-- Generated by htmldoc --></HEAD><BODY BGCOLOR="#ffffff" LINK="#0000ee" TEXT="#000000" VLINK="#551a8b" ALINK="#ff0000"> <IMG SRC="CorpID.gif" ALT="SGI" HEIGHT="43" WIDTH="151"> <!--end header--><BR Clear><H1>set_symmetric_difference</H1><Table CellPadding=0 CellSpacing=0 width=100%><TR><TD Align=left><Img src = "algorithms.gif" Alt="" WIDTH = "194" HEIGHT = "38" ></TD><TD Align=right><Img src = "function.gif" Alt="" WIDTH = "194" HEIGHT = "38" ></TD></TR><TR><TD Align=left VAlign=top><b>Category</b>: algorithms</TD><TD Align=right VAlign=top><b>Component type</b>: function</TD></TR></Table><h3>Prototype</h3><tt>Set_symmetric_difference</tt> is an overloaded name; there are actually two <tt>set_symmetric_difference</tt> functions.<pre>template <class <A href="InputIterator.html">InputIterator</A>1, class <A href="InputIterator.html">InputIterator</A>2, class <A href="OutputIterator.html">OutputIterator</A>>OutputIterator set_symmetric_difference(InputIterator1 first1, InputIterator1 last1, InputIterator2 first2, InputIterator2 last2, OutputIterator result);template <class <A href="InputIterator.html">InputIterator</A>1, class <A href="InputIterator.html">InputIterator</A>2, class <A href="OutputIterator.html">OutputIterator</A>, class <A href="StrictWeakOrdering.html">StrictWeakOrdering</A>>OutputIterator set_symmetric_difference(InputIterator1 first1, InputIterator1 last1, InputIterator2 first2, InputIterator2 last2, OutputIterator result, StrictWeakOrdering comp);</pre> <h3>Description</h3><tt>Set_symmetric_difference</tt> constructs a sorted range that is the set symmetricdifference of the sorted ranges <tt>[first1, last1)</tt> and <tt>[first2,last2)</tt>. The return value is the end of the output range.<P>In the simplest case, <tt>set_symmetric_difference</tt> performs a settheoretic calculation: it constructs the union of the two sets <tt>A - B</tt>and <tt>B - A</tt>, where <tt>A</tt> and <tt>B</tt> are the two input ranges. That is, theoutput range contains a copy of every element that is contained in<tt>[first1, last1)</tt> but not <tt>[first2, last2)</tt>, and a copy of every elementthat is contained in <tt>[first2, last2)</tt> but not <tt>[first1, last1)</tt>. The general case is more complicated, because the input ranges maycontain duplicate elements. The generalization is that if a valueappears <tt>m</tt> times in <tt>[first1, last1)</tt> and <tt>n</tt> times in <tt>[first2,last2)</tt> (where <tt>m</tt> or <tt>n</tt> may be zero), then it appears <tt>|m-n|</tt>times in the output range. <A href="#1">[1]</A> <tt>Set_symmetric_difference</tt> is stable, meaning that the relative order of elements within each input range is preserved.<P>The two versions of <tt>set_symmetric_difference</tt> differ in how they define whether one element is less than another. The first versioncompares objects using <tt>operator<</tt>, and the second compares objects using a <A href="functors.html">function object</A> <tt>comp</tt>.<h3>Definition</h3>Defined in the standard header <A href="algorithm">algorithm</A>, and in the nonstandardbackward-compatibility header <A href="algo.h">algo.h</A>.<h3>Requirements on types</h3>For the first version:<UL><LI><tt>InputIterator1</tt> is a model of <A href="InputIterator.html">Input Iterator</A>.<LI><tt>InputIterator2</tt> is a model of <A href="InputIterator.html">Input Iterator</A>.<LI><tt>OutputIterator</tt> is a model of <A href="OutputIterator.html">Output Iterator</A>.<LI><tt>InputIterator1</tt> and <tt>InputIterator2</tt> have the same value type.<LI><tt>InputIterator</tt>'s value type is a model of <A href="LessThanComparable.html">LessThan Comparable</A>.<LI>The ordering on objects of <tt>InputIterator1</tt>'s value type is a <i>strict weak ordering</i>, as defined in the <A href="LessThanComparable.html">LessThan Comparable</A> requirements.<LI><tt>InputIterator</tt>'s value type is convertible to a type in <tt>OutputIterator</tt>'s set of value types.</UL>For the second version:<UL><LI><tt>InputIterator1</tt> is a model of <A href="InputIterator.html">Input Iterator</A>.<LI><tt>InputIterator2</tt> is a model of <A href="InputIterator.html">Input Iterator</A>.<LI><tt>OutputIterator</tt> is a model of <A href="OutputIterator.html">Output Iterator</A>.<LI><tt>StrictWeakOrdering</tt> is a model of <A href="StrictWeakOrdering.html">Strict Weak Ordering</A>.<LI><tt>InputIterator1</tt> and <tt>InputIterator2</tt> have the same value type.<LI><tt>InputIterator1</tt>'s value type is convertible to <tt>StrictWeakOrdering</tt>'s argument type.<LI><tt>InputIterator</tt>'s value type is convertible to a type in <tt>OutputIterator</tt>'s set of value types.</UL><h3>Preconditions</h3>For the first version:<UL><LI><tt>[first1, last1)</tt> is a valid range.<LI><tt>[first2, last2)</tt> is a valid range.<LI><tt>[first1, last1)</tt> is ordered in ascending order according to <tt>operator<</tt>. That is, for every pair of iterators <tt>i</tt> and <tt>j</tt> in <tt>[first1, last1)</tt> such that <tt>i</tt> precedes <tt>j</tt>, <tt>*j < *i</tt> is <tt>false</tt>.<LI><tt>[first2, last2)</tt> is ordered in ascending order according to <tt>operator<</tt>. That is, for every pair of iterators <tt>i</tt> and <tt>j</tt> in <tt>[first2, last2)</tt> such that <tt>i</tt> precedes <tt>j</tt>, <tt>*j < *i</tt> is <tt>false</tt>.<LI>There is enough space to hold all of the elements being copied. More formally, the requirement is that <tt>[result, result + n)</tt> is a valid range, where <tt>n</tt> is the number of elements in the symmetric difference of the two input ranges.<LI><tt>[first1, last1)</tt> and <tt>[result, result + n)</tt> do not overlap.<LI><tt>[first2, last2)</tt> and <tt>[result, result + n)</tt> do not overlap.</UL>For the second version:<UL><LI><tt>[first1, last1)</tt> is a valid range.<LI><tt>[first2, last2)</tt> is a valid range.<LI><tt>[first1, last1)</tt> is ordered in ascending order according to <tt>comp</tt>. That is, for every pair of iterators <tt>i</tt> and <tt>j</tt> in <tt>[first1, last1)</tt> such that <tt>i</tt> precedes <tt>j</tt>, <tt>comp(*j, *i)</tt> is <tt>false</tt>.<LI><tt>[first2, last2)</tt> is ordered in ascending order according to <tt>comp</tt>. That is, for every pair of iterators <tt>i</tt> and <tt>j</tt> in <tt>[first2, last2)</tt> such that <tt>i</tt> precedes <tt>j</tt>, <tt>comp(*j, *i)</tt> is <tt>false</tt>.<LI>There is enough space to hold all of the elements being copied. More formally, the requirement is that <tt>[result, result + n)</tt> is a valid range, where <tt>n</tt> is the number of elements in the symmetric difference of the two input ranges.<LI><tt>[first1, last1)</tt> and <tt>[result, result + n)</tt> do not overlap.<LI><tt>[first2, last2)</tt> and <tt>[result, result + n)</tt> do not overlap.</UL><h3>Complexity</h3>Linear. Zero comparisons if either <tt>[first1, last1)</tt> or <tt>[first2, last2)</tt>is empty, otherwise at most <tt>2 * ((last1 - first1) + (last2 - first2))- 1</tt> comparisons.<h3>Example</h3><pre>inline bool lt_nocase(char c1, char c2) { return tolower(c1) < tolower(c2); }int main(){ int A1[] = {1, 3, 5, 7, 9, 11}; int A2[] = {1, 1, 2, 3, 5, 8, 13}; char A3[] = {'a', 'b', 'b', 'B', 'B', 'f', 'g', 'h', 'H'}; char A4[] = {'A', 'B', 'B', 'C', 'D', 'F', 'F', 'H' }; const int N1 = sizeof(A1) / sizeof(int); const int N2 = sizeof(A2) / sizeof(int); const int N3 = sizeof(A3); const int N4 = sizeof(A4); cout << "Symmetric difference of A1 and A2: "; set_symmetric_difference(A1, A1 + N1, A2, A2 + N2, ostream_iterator<int>(cout, " ")); cout << endl << "Symmetric difference of A3 and A4: "; set_symmetric_difference(A3, A3 + N3, A4, A4 + N4, ostream_iterator<char>(cout, " "), lt_nocase); cout << endl;}</pre><P>The output is<pre>Symmetric difference of A1 and A2: 1 2 7 8 9 11 13 Symmetric difference of A3 and A4: B B C D F g H </pre><h3>Notes</h3><P><A name="1">[1]</A>Even this is not a completely precise description, becausethe ordering by which the input ranges are sortedis permitted to be a strict weak ordering that is not a total ordering:there might bevalues <tt>x</tt> and <tt>y</tt> that are equivalent (that is, neither <tt>x < y</tt> nor<tt>y < x</tt>) but not equal. See the <A href="LessThanComparable.html">LessThan Comparable</A>requirements for a more complete discussion. The output range consists ofthose elements from <tt>[first1, last1)</tt> for which equivalent elements donot exist in <tt>[first2, last2)</tt>, and those elements from <tt>[first2, last2)</tt> for which equivalent elements donot exist in <tt>[first1, last1)</tt>.Specifically, suppose that the range<tt>[first1, last1)</tt> contains <tt>m</tt> elements that are equivalent to eachother and the range <tt>[first2, last2)</tt> contains <tt>n</tt> elements from thatequivalence class (where either <tt>m</tt> or <tt>n</tt> may be zero). If <tt>m > n</tt>then the output range contains the <i>last</i> <tt>m - n</tt> of theseelements elements from <tt>[first1, last1)</tt>, and if <tt>m < n</tt> then theoutput range contains the last <tt>n - m</tt> of these elements elementsfrom <tt>[first2, last2)</tt>.<h3>See also</h3><tt><A href="includes.html">includes</A></tt>, <tt><A href="set_union.html">set_union</A></tt>, <tt><A href="set_intersection.html">set_intersection</A></tt>, <tt><A href="set_difference.html">set_difference</A></tt>, <tt><A href="sort.html">sort</A></tt><!--start footer--> <HR SIZE="6"><A href="http://www.sgi.com/"><IMG SRC="surf.gif" HEIGHT="54" WIDTH="54" ALT="[Silicon Surf]"></A><A HREF="index.html"><IMG SRC="stl_home.gif" HEIGHT="54" WIDTH="54" ALT="[STL Home]"></A><BR><FONT SIZE="-2"><A href="http://www.sgi.com/Misc/sgi_info.html" TARGET="_top">Copyright © 1999 Silicon Graphics, Inc.</A> All Rights Reserved.</FONT><FONT SIZE="-3"><a href="http://www.sgi.com/Misc/external.list.html" TARGET="_top">TrademarkInformation</A></FONT><P></BODY></HTML> ?? 快捷鍵說明
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