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<HTML><!-- -- Copyright (c) 1996-1999 -- Silicon Graphics Computer Systems, Inc. -- -- Permission to use, copy, modify, distribute and sell this software -- and its documentation for any purpose is hereby granted without fee, -- provided that the above copyright notice appears in all copies and -- that both that copyright notice and this permission notice appear -- in supporting documentation. Silicon Graphics makes no -- representations about the suitability of this software for any -- purpose. It is provided "as is" without express or implied warranty. -- -- Copyright (c) 1994 -- Hewlett-Packard Company -- -- Permission to use, copy, modify, distribute and sell this software -- and its documentation for any purpose is hereby granted without fee, -- provided that the above copyright notice appears in all copies and -- that both that copyright notice and this permission notice appear -- in supporting documentation. 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It is provided "as is" without express or implied warranty. -- --><Head><Title>merge</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>merge</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>Merge</tt> is an overloaded name: there are actually two <tt>merge</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 merge(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 merge(InputIterator1 first1, InputIterator1 last1, InputIterator2 first2, InputIterator2 last2, OutputIterator result, StrictWeakOrdering comp);</pre> <h3>Description</h3><tt>Merge</tt> combines two sorted ranges <tt>[first1, last1)</tt> and <tt>[first2, last2)</tt> into a single sorted range. That is, it copieselements from <tt>[first1, last1)</tt> and <tt>[first2, last2)</tt> into<tt>[result, result + (last1 - first1) + (last2 - first2))</tt> such thatthe resulting range is in ascending order. <tt>Merge</tt> is stable, meaning both thatthe relative order of elements within each input range is preserved, and that for equivalent <A href="#1">[1]</A> elements in both input ranges the elementfrom the first range precedes the element from the second.The return value is <tt>result + (last1 - first1) + (last2 - first2)</tt>.<P>The two versions of <tt>merge</tt> differ in how elements are compared.The first version uses <tt>operator<</tt>. That is, the input ranges andthe output range satisfy the condition that for every pair of iterators <tt>i</tt> and <tt>j</tt> such that <tt>i</tt> precedes <tt>j</tt>, <tt>*j < *i</tt> is <tt>false</tt>.The second version uses the <A href="functors.html">function object</A> <tt>comp</tt>. That is, the input ranges and the output range satisfy the condition that for every pair of iterators <tt>i</tt> and <tt>j</tt> such that <tt>i</tt> precedes <tt>j</tt>, <tt>comp(*j, *i)</tt> is <tt>false</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>InputIterator1</tt>'s value type is the same type as <tt>InputIterator2</tt>'s value type.<LI><tt>InputIterator1</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>InputIterator1</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>InputIterator1</tt>'s value type is the same type as <tt>InputIterator2</tt>'s value type.<LI><tt>StrictWeakOrdering</tt> is a model of <A href="StrictWeakOrdering.html">Strict Weak Ordering</A>.<LI><tt>InputIterator1</tt>'s value type is convertible to <tt>StrictWeakOrdering</tt>'s argument type.<LI><tt>InputIterator1</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>[first1, last1)</tt> is in ascending order. 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 a valid range.<LI><tt>[first2, last2)</tt> is in ascending order. 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>The ranges <tt>[first1, last1)</tt> and <tt>[result, result + (last1 - first1) + (last2 - first2))</tt> do not overlap.<LI>The ranges <tt>[first2, last2)</tt> and <tt>[result, result + (last1 - first1) + (last2 - first2))</tt> do not overlap.<LI>There is enough space to hold all of the elements being copied. More formally, the requirement is that <tt>[result, result + (last1 - first1) + (last2 - first2))</tt> is a valid range. </UL>For the second version:<UL><LI><tt>[first1, last1)</tt> is a valid range.<LI><tt>[first1, last1)</tt> is in ascending order. 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 a valid range.<LI><tt>[first2, last2)</tt> is in ascending order. 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>The ranges <tt>[first1, last1)</tt> and <tt>[result, result + (last1 - first1) + (last2 - first2))</tt> do not overlap.<LI>The ranges <tt>[first2, last2)</tt> and <tt>[result, result + (last1 - first1) + (last2 - first2))</tt> do not overlap.<LI>There is enough space to hold all of the elements being copied. More formally, the requirement is that <tt>[result, result + (last1 - first1) + (last2 - first2))</tt> is a valid range. </UL><h3>Complexity</h3>Linear. No comparisons if both <tt>[first1, last1)</tt> and <tt>[first2, last2)</tt>are empty ranges, otherwise at most <tt>(last1 - first1) + (last2 -first2) - 1</tt> comparisons.<h3>Example</h3><pre>int main(){ int A1[] = { 1, 3, 5, 7 }; int A2[] = { 2, 4, 6, 8 }; const int N1 = sizeof(A1) / sizeof(int); const int N2 = sizeof(A2) / sizeof(int); merge(A1, A1 + N1, A2, A2 + N2, <A href="ostream_iterator.html">ostream_iterator</A><int>(cout, " ")); // The output is "1 2 3 4 5 6 7 8"}</pre><h3>Notes</h3><P><A name="1">[1]</A>Note that you may use an ordering that is a strict weak orderingbut not a total ordering; that is, there might be values <tt>x</tt> and <tt>y</tt>such that <tt>x < y</tt>, <tt>x > y</tt>, and <tt>x == y</tt> are all false. (See the<A href="LessThanComparable.html">LessThan Comparable</A> requirements for a more complete discussion.)Two elements <tt>x</tt> and <tt>y</tt> are <i>equivalent</i> if neither <tt>x < y</tt> nor<tt>y < x</tt>. If you're using a total ordering, however (if you'reusing <tt>strcmp</tt>, for example, or if you're using ordinary arithmeticcomparison on integers), then you can ignore this technicaldistinction: for a total ordering, equality and equivalence arethe same.<h3>See also</h3><tt><A href="inplace_merge.html">inplace_merge</A></tt>, <tt><A href="set_union.html">set_union</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> ⌨️ 快捷键说明
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