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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>make_heap</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>make_heap</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>Make_heap</tt> is an overloaded name; there are actually two <tt>make_heap</tt> functions. <pre>template <class <A href="RandomAccessIterator.html">RandomAccessIterator</A>>void make_heap(RandomAccessIterator first, RandomAccessIterator last);template <class <A href="RandomAccessIterator.html">RandomAccessIterator</A>, class <A href="StrictWeakOrdering.html">StrictWeakOrdering</A>>void make_heap(RandomAccessIterator first, RandomAccessIterator last, StrictWeakOrdering comp);</pre> <h3>Description</h3><tt>Make_heap</tt> turns the range <tt>[first, last)</tt> into a heap <A href="#1">[1]</A>. <P>The two versions of <tt>make_heap</tt> differ in how they define whether oneelement is less than another. The first version comparesobjects using <tt>operator<</tt>, and the second compares objects usinga <A href="functors.html">function object</A> <tt>comp</tt>.In the first version the postcondition is that <tt><A href="is_heap.html">is_heap</A>(first, last)</tt>is <tt>true</tt>, and in the second version the postcondition is that <tt><A href="is_heap.html">is_heap</A>(first, last, comp)</tt> is <tt>true</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>RandomAccessIterator</tt> is a model of <A href="RandomAccessIterator.html">Random Access Iterator</A>.<LI><tt>RandomAccessIterator</tt> is mutable.<LI><tt>RandomAccessIterator</tt>'s value type is a model of <A href="LessThanComparable.html">LessThan Comparable</A>.<LI>The ordering on objects of <tt>RandomAccessIterator</tt>'s value type is a <i>strict weak ordering</i>, as defined in the <A href="LessThanComparable.html">LessThan Comparable</A> requirements.</UL>For the second version:<UL><LI><tt>RandomAccessIterator</tt> is a model of <A href="RandomAccessIterator.html">Random Access Iterator</A>.<LI><tt>RandomAccessIterator</tt> is mutable.<LI><tt>StrictWeakOrdering</tt> is a model of <A href="StrictWeakOrdering.html">Strict Weak Ordering</A>.<LI><tt>RandomAccessIterator</tt>'s value type is convertible to <tt>StrictWeakOrdering</tt>'s argument type.</UL><h3>Preconditions</h3><UL><LI><tt>[first, last)</tt> is a valid range.</UL><h3>Complexity</h3>Linear. At most <tt>3*(last - first)</tt> comparisons.<h3>Example</h3><pre>int main(){ int A[] = {1, 4, 2, 8, 5, 7}; const int N = sizeof(A) / sizeof(int); make_heap(A, A+N); <A href="copy.html">copy</A>(A, A+N, <A href="ostream_iterator.html">ostream_iterator</A><int>(cout, " ")); cout << endl; <A href="sort_heap.html">sort_heap</A>(A, A+N); <A href="copy.html">copy</A>(A, A+N, <A href="ostream_iterator.html">ostream_iterator</A><int>(cout, " ")); cout << endl;}</pre><h3>Notes</h3><P><A name="1">[1]</A>A heap is a particular way of ordering the elements in a range of<A href="RandomAccessIterator.html">Random Access Iterators</A> <tt>[f, l)</tt>. The reason heaps are useful(especially for sorting, or as priority queues) is that they satisfytwo important properties. First, <tt>*f</tt> is the largest element in theheap. Second, it is possible to add an element to a heap (using<tt>push_heap</tt>), or to remove <tt>*f</tt>, in logarithmic time.Internally, a heap is simply a tree represented as a sequential range.The tree is constructed so that that eachnode is less than or equal to its parent node.<h3>See also</h3><tt><A href="push_heap.html">push_heap</A></tt>, <tt><A href="pop_heap.html">pop_heap</A></tt>, <tt><A href="sort_heap.html">sort_heap</A></tt>, <tt><A href="sort.html">sort</A></tt>, <tt><A href="is_heap.html">is_heap</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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