📄 page183.html

📁 wqeqwvrw rkjqhwrjwq jkhrjqwhrwq jkhrwq
💻 HTML
字号:
<HTML>
<HEAD>
<TITLE>Finding the Position of an Item and Accessing by Position</TITLE>
</HEAD>
<BODY bgcolor="#FFFFFF">
 <img src="cover75.gif" tppabs="http://dictator.uwaterloo.ca/Bruno.Preiss/books/opus4/icons/cover75.gif" alt="Logo" align=right>
<b>Data Structures and Algorithms 
with Object-Oriented Design Patterns in C++</b><br>
<A NAME="tex2html4177" HREF="page184.html" tppabs="http://dictator.uwaterloo.ca/Bruno.Preiss/books/opus4/html/page184.html"><IMG WIDTH=37 HEIGHT=24 ALIGN=BOTTOM ALT="next" SRC="next_motif.gif" tppabs="http://dictator.uwaterloo.ca/Bruno.Preiss/books/opus4/icons/next_motif.gif"></A> <A NAME="tex2html4175" HREF="page177.html" tppabs="http://dictator.uwaterloo.ca/Bruno.Preiss/books/opus4/html/page177.html"><IMG WIDTH=26 HEIGHT=24 ALIGN=BOTTOM ALT="up" SRC="up_motif.gif" tppabs="http://dictator.uwaterloo.ca/Bruno.Preiss/books/opus4/icons/up_motif.gif"></A> <A NAME="tex2html4169" HREF="page182.html" tppabs="http://dictator.uwaterloo.ca/Bruno.Preiss/books/opus4/html/page182.html"><IMG WIDTH=63 HEIGHT=24 ALIGN=BOTTOM ALT="previous" SRC="previous_motif.gif" tppabs="http://dictator.uwaterloo.ca/Bruno.Preiss/books/opus4/icons/previous_motif.gif"></A> <A NAME="tex2html4179" HREF="page9.html" tppabs="http://dictator.uwaterloo.ca/Bruno.Preiss/books/opus4/html/page9.html"><IMG WIDTH=65 HEIGHT=24 ALIGN=BOTTOM ALT="contents" SRC="contents_motif.gif" tppabs="http://dictator.uwaterloo.ca/Bruno.Preiss/books/opus4/icons/contents_motif.gif"></A> <A NAME="tex2html4180" HREF="page620.html" tppabs="http://dictator.uwaterloo.ca/Bruno.Preiss/books/opus4/html/page620.html"><IMG WIDTH=43 HEIGHT=24 ALIGN=BOTTOM ALT="index" SRC="index_motif.gif" tppabs="http://dictator.uwaterloo.ca/Bruno.Preiss/books/opus4/icons/index_motif.gif"></A> <BR><HR>
<H3><A NAME="SECTION008126000000000000000">Finding the Position of an Item and Accessing by Position</A></H3>
<P>
The <tt>FindPosition</tt> member function of the <tt>ListAsLinkedList</tt>
class is used to determine the position of an item in an ordered list
implemented as a linked list.
Its result is a reference to a <tt>Position</tt>.
Such a position can be used with the subscripting operator,
<tt>operator[]</tt> to access the item in the ordered list
found at the given position.
The <tt>FindPosition</tt> and <tt>operator[]</tt> member functions
are defined in Program&nbsp;<A HREF="page183.html#proglist10c" tppabs="http://dictator.uwaterloo.ca/Bruno.Preiss/books/opus4/html/page183.html#proglist10c"><IMG  ALIGN=BOTTOM ALT="gif" SRC="cross_ref_motif.gif" tppabs="http://dictator.uwaterloo.ca/Bruno.Preiss/books/opus4/icons/cross_ref_motif.gif"></A>
<P>
<P><A NAME="10559">&#160;</A><A NAME="proglist10c">&#160;</A> <IMG WIDTH=575 HEIGHT=372 ALIGN=BOTTOM ALT="program10239" SRC="img808.gif" tppabs="http://dictator.uwaterloo.ca/Bruno.Preiss/books/opus4/html/img808.gif"  ><BR>
<STRONG>Program:</STRONG> <tt>ListAsLinkedList</tt> Class <tt>FindPosition</tt> Member Function 	and Subscripting Operator Definitions<BR>
<P>
<P>
The <tt>FindPosition</tt> function takes as its lone argument
a <tt>const</tt> reference to an <tt>Object</tt> that is the target of the search.
The search algorithm used by <tt>FindPosition</tt> is identical to that of
<tt>Find</tt>, which is given in Program&nbsp;<A HREF="page180.html#proglist8c" tppabs="http://dictator.uwaterloo.ca/Bruno.Preiss/books/opus4/html/page180.html#proglist8c"><IMG  ALIGN=BOTTOM ALT="gif" SRC="cross_ref_motif.gif" tppabs="http://dictator.uwaterloo.ca/Bruno.Preiss/books/opus4/icons/cross_ref_motif.gif"></A>.
Consequently, the running time is the same:
<P> <IMG WIDTH=338 HEIGHT=17 ALIGN=BOTTOM ALT="displaymath61730" SRC="img809.gif" tppabs="http://dictator.uwaterloo.ca/Bruno.Preiss/books/opus4/html/img809.gif"  ><P>
where  <IMG WIDTH=89 HEIGHT=26 ALIGN=MIDDLE ALT="tex2html_wrap_inline61648" SRC="img789.gif" tppabs="http://dictator.uwaterloo.ca/Bruno.Preiss/books/opus4/html/img789.gif"  > is the time required to match to <tt>Object</tt>s,
and  <IMG WIDTH=72 HEIGHT=9 ALIGN=BOTTOM ALT="tex2html_wrap_inline61308" SRC="img709.gif" tppabs="http://dictator.uwaterloo.ca/Bruno.Preiss/books/opus4/html/img709.gif"  > is the number of items in the ordered list.
<P>
The subscripting operator, <tt>operator[]</tt>,
which takes as its subscript expression a reference to
a <tt>Position</tt> is also defined in Program&nbsp;<A HREF="page183.html#proglist10c" tppabs="http://dictator.uwaterloo.ca/Bruno.Preiss/books/opus4/html/page183.html#proglist10c"><IMG  ALIGN=BOTTOM ALT="gif" SRC="cross_ref_motif.gif" tppabs="http://dictator.uwaterloo.ca/Bruno.Preiss/books/opus4/icons/cross_ref_motif.gif"></A>.
This routine assumes that the position it is passed is
an instance of a <tt>ListAsLinkedList::Pos</tt>.
It simply dereferences the <tt>element</tt> pointer
contained in the <tt>ListAsLinkedList::Pos</tt> argument
to obtain the required item in the ordered list. 
Assuming no exceptions are thrown,
the running time is clearly <I>O</I>(1).
<P>
<HR><A NAME="tex2html4177" HREF="page184.html" tppabs="http://dictator.uwaterloo.ca/Bruno.Preiss/books/opus4/html/page184.html"><IMG WIDTH=37 HEIGHT=24 ALIGN=BOTTOM ALT="next" SRC="next_motif.gif" tppabs="http://dictator.uwaterloo.ca/Bruno.Preiss/books/opus4/icons/next_motif.gif"></A> <A NAME="tex2html4175" HREF="page177.html" tppabs="http://dictator.uwaterloo.ca/Bruno.Preiss/books/opus4/html/page177.html"><IMG WIDTH=26 HEIGHT=24 ALIGN=BOTTOM ALT="up" SRC="up_motif.gif" tppabs="http://dictator.uwaterloo.ca/Bruno.Preiss/books/opus4/icons/up_motif.gif"></A> <A NAME="tex2html4169" HREF="page182.html" tppabs="http://dictator.uwaterloo.ca/Bruno.Preiss/books/opus4/html/page182.html"><IMG WIDTH=63 HEIGHT=24 ALIGN=BOTTOM ALT="previous" SRC="previous_motif.gif" tppabs="http://dictator.uwaterloo.ca/Bruno.Preiss/books/opus4/icons/previous_motif.gif"></A> <A NAME="tex2html4179" HREF="page9.html" tppabs="http://dictator.uwaterloo.ca/Bruno.Preiss/books/opus4/html/page9.html"><IMG WIDTH=65 HEIGHT=24 ALIGN=BOTTOM ALT="contents" SRC="contents_motif.gif" tppabs="http://dictator.uwaterloo.ca/Bruno.Preiss/books/opus4/icons/contents_motif.gif"></A> <A NAME="tex2html4180" HREF="page620.html" tppabs="http://dictator.uwaterloo.ca/Bruno.Preiss/books/opus4/html/page620.html"><IMG WIDTH=43 HEIGHT=24 ALIGN=BOTTOM ALT="index" SRC="index_motif.gif" tppabs="http://dictator.uwaterloo.ca/Bruno.Preiss/books/opus4/icons/index_motif.gif"></A> <P><ADDRESS>
<img src="bruno.gif" tppabs="http://dictator.uwaterloo.ca/Bruno.Preiss/books/opus4/icons/bruno.gif" alt="Bruno" align=right>
<a href="javascript:if(confirm('http://dictator.uwaterloo.ca/Bruno.Preiss/books/opus4/copyright.html  \n\nThis file was not retrieved by Teleport Pro, because it is addressed on a domain or path outside the boundaries set for its Starting Address.  \n\nDo you want to open it from the server?'))window.location='http://dictator.uwaterloo.ca/Bruno.Preiss/books/opus4/copyright.html'" tppabs="http://dictator.uwaterloo.ca/Bruno.Preiss/books/opus4/copyright.html">Copyright &#169; 1997</a> by <a href="javascript:if(confirm('http://dictator.uwaterloo.ca/Bruno.Preiss/books/opus4/signature.html  \n\nThis file was not retrieved by Teleport Pro, because it is addressed on a domain or path outside the boundaries set for its Starting Address.  \n\nDo you want to open it from the server?'))window.location='http://dictator.uwaterloo.ca/Bruno.Preiss/books/opus4/signature.html'" tppabs="http://dictator.uwaterloo.ca/Bruno.Preiss/books/opus4/signature.html">Bruno R. Preiss, P.Eng.</a>  All rights reserved.

</ADDRESS>
</BODY>
</HTML>
⌨️ 快捷键说明

复制代码 Ctrl + C
搜索代码 Ctrl + F
全屏模式 F11
切换主题 Ctrl + Shift + D
显示快捷键 ?
增大字号 Ctrl + =
减小字号 Ctrl + -