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It is provided "as is" without express or implied warranty. -- --><Head><Title>push_heap</Title><!-- Generated by htmldoc --></HEAD><BODY TEXT="#000000" LINK="#006600" ALINK="#003300" VLINK="#7C7F87" BGCOLOR="#FFFFFF"><A HREF="/"><IMG SRC="/images/common/sgilogo_small.gif" ALT="SGI Logo" WIDTH="80" HEIGHT="72" BORDER="0"></A><P><!--end header--><BR Clear><H1>push_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>Push_heap</tt> is an overloaded name; there are actually two <tt>push_heap</tt> functions. <pre>template <class <A href="RandomAccessIterator.html">RandomAccessIterator</A>>void push_heap(RandomAccessIterator first, RandomAccessIterator last);template <class <A href="RandomAccessIterator.html">RandomAccessIterator</A>, class <A href="StrictWeakOrdering.html">StrictWeakOrdering</A>>void push_heap(RandomAccessIterator first, RandomAccessIterator last, StrictWeakOrdering comp);</pre> <h3>Description</h3><tt>Push_heap</tt> adds an element to a heap <A href="#1">[1]</A>. It is assumed that <tt>[first, last - 1)</tt> is already a heap; the element to be added tothe heap is <tt>*(last - 1)</tt>. <P>The two versions of <tt>push_heap</tt> differ in how they define whether oneelement is less than another. The first version compares objectsusing <tt>operator<</tt>, and the second compares objects using a <A href="functors.html">function object</A> <tt>comp</tt>. The postcondition for the first versionis that <tt><A href="is_heap.html">is_heap</A>(first, last)</tt> is <tt>true</tt>, and the postconditionfor the second version 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>For the first version:<UL><LI><tt>[first, last)</tt> is a valid range.<LI><tt>[first, last - 1)</tt> is a valid range. That is, <tt>[first, last)</tt> is nonempty.<LI><tt>[first, last - 1)</tt> is a heap. That is, <tt><A href="is_heap.html">is_heap</A>(first, last - 1)</tt> is <tt>true</tt>.</UL>For the second version:<UL><LI><tt>[first, last)</tt> is a valid range.<LI><tt>[first, last - 1)</tt> is a valid range. That is, <tt>[first, last)</tt> is nonempty.<LI><tt>[first, last)</tt> is a heap. That is, <tt><A href="is_heap.html">is_heap</A>(first, last - 1, comp)</tt> is <tt>true</tt>.</UL><h3>Complexity</h3>Logarithmic. At most <tt>log(last - first)</tt> comparisons.<h3>Example</h3><pre>int main(){ int A[10] = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9 }; <A href="make_heap.html">make_heap</A>(A, A + 9); cout << "[A, A + 9) = "; <A href="copy.html">copy</A>(A, A + 9, <A href="ostream_iterator.html">ostream_iterator</A><int>(cout, " ")); push_heap(A, A + 10); cout << endl << "[A, A + 10) = "; <A href="copy.html">copy</A>(A, A + 10, <A href="ostream_iterator.html">ostream_iterator</A><int>(cout, " ")); cout << endl;}</pre><P>The output is <pre>[A, A + 9) = 8 7 6 3 4 5 2 1 0 [A, A + 10) = 9 8 6 3 7 5 2 1 0 4 </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 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="make_heap.html">make_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="is_heap.html">is_heap</A></tt>, <tt><A href="sort.html">sort</A></tt><!-- start footer --><!-- Footer Begins --><STYLE TYPE="text/css"><!--TD.footer, TD.footer A{ font-family: Arial, helvetica, sans-serif; font-size: 8pt;}A.home {font-family: Arial, helvetica, sans-serif;}--></STYLE><P><A CLASS="home" HREF="index.html">STL Home</A><P><TABLE WIDTH="600" CELLPADDING="0" CELLPADDING="0" BORDER="0"> <TR> <TD ALIGN="RIGHT" CLASS="footer"><A HREF="/company_info/terms.html" TARGET="_top">terms of use</A> | <A HREF="/company_info/privacy.html" TARGET="_top">privacy policy</A></TD> <TD ALIGN="CENTER" CLASS="footer"> | </TD> <TD ALIGN="LEFT" CLASS="footer"><A HREF="/cgi-bin/feedback/" TARGET="_top">contact us</A></TD> </TR><TR> <TD ALIGN="RIGHT" CLASS="footer">Copyright © 1993-2003 Silicon Graphics, Inc. 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