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<b>Data Structures and Algorithms
with Object-Oriented Design Patterns in C++</b><br>
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<H3><A NAME="SECTION009412000000000000000">Constructor and Destructor</A></H3>
<P>
The constructor and destructor for the <tt>ChainedHashTable</tt>
class are defined in Program <A HREF="page225.html#proghashtbl2c" tppabs="http://dictator.uwaterloo.ca/Bruno.Preiss/books/opus4/html/page225.html#proghashtbl2c"><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>.
The constructor takes a single argument of type <tt>unsigned int</tt>
which specifies the size of hash table desired.
The constructor simply initializes the <tt>HashTable</tt> base class
and the <tt>array</tt> member variable accordingly.
Initializing the <tt>array</tt> variable involves constructing
the required number of empty linked lists.
Consequently, the running time for the <tt>ChainedHashTable</tt>
constructor is <I>O</I>(<I>M</I>) where <I>M</I> is the size of the hash table.
<P>
<P><A NAME="12071"> </A><A NAME="proghashtbl2c"> </A> <IMG WIDTH=575 HEIGHT=469 ALIGN=BOTTOM ALT="program11924" SRC="img971.gif" tppabs="http://dictator.uwaterloo.ca/Bruno.Preiss/books/opus4/html/img971.gif" ><BR>
<STRONG>Program:</STRONG> <tt>ChainedHashTable</tt> Class Constructor, Destructor and <tt>Purge</tt> Member Function Definitions<BR>
<P>
<P>
The <tt>ChainedHashTable</tt> destructor
simply calls the <tt>Purge</tt> member function.
Since the <tt>ChainedHashTable</tt> is a container,
the <tt>Purge</tt> function must delete any contained objects
if it is the owner of those objects.
Therefore, the <tt>Purge</tt> function is required to traverse
each of the linked lists in the array.
<P>
To determine the running time of the <tt>Purge</tt> function,
we will assume that there are <I>n</I> contained objects
and the length of the array is <I>M</I>.
Furthermore, let <IMG WIDTH=13 HEIGHT=15 ALIGN=MIDDLE ALT="tex2html_wrap_inline62818" SRC="img972.gif" tppabs="http://dictator.uwaterloo.ca/Bruno.Preiss/books/opus4/html/img972.gif" > be the number of items
in the <IMG WIDTH=17 HEIGHT=13 ALIGN=BOTTOM ALT="tex2html_wrap_inline58387" SRC="img77.gif" tppabs="http://dictator.uwaterloo.ca/Bruno.Preiss/books/opus4/html/img77.gif" > linked list
for <IMG WIDTH=132 HEIGHT=22 ALIGN=MIDDLE ALT="tex2html_wrap_inline62822" SRC="img973.gif" tppabs="http://dictator.uwaterloo.ca/Bruno.Preiss/books/opus4/html/img973.gif" >.
Note that <IMG WIDTH=94 HEIGHT=33 ALIGN=MIDDLE ALT="tex2html_wrap_inline62824" SRC="img974.gif" tppabs="http://dictator.uwaterloo.ca/Bruno.Preiss/books/opus4/html/img974.gif" >.
The running time of the inner loop
for the <IMG WIDTH=17 HEIGHT=13 ALIGN=BOTTOM ALT="tex2html_wrap_inline58387" SRC="img77.gif" tppabs="http://dictator.uwaterloo.ca/Bruno.Preiss/books/opus4/html/img77.gif" > iteration of the outer loop
is <IMG WIDTH=193 HEIGHT=26 ALIGN=MIDDLE ALT="tex2html_wrap_inline62828" SRC="img975.gif" tppabs="http://dictator.uwaterloo.ca/Bruno.Preiss/books/opus4/html/img975.gif" >.
The constant overhead arises from the loop termination test
which must be done at least once.
The total running time of the destructor is given by
<P> <IMG WIDTH=475 HEIGHT=47 ALIGN=BOTTOM ALT="displaymath62808" SRC="img976.gif" tppabs="http://dictator.uwaterloo.ca/Bruno.Preiss/books/opus4/html/img976.gif" ><P>
If we assume that <IMG WIDTH=120 HEIGHT=26 ALIGN=MIDDLE ALT="tex2html_wrap_inline62830" SRC="img977.gif" tppabs="http://dictator.uwaterloo.ca/Bruno.Preiss/books/opus4/html/img977.gif" >,
the running time simplifies to <I>O</I>(<I>M</I>+<I>n</I>).
<P>
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