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<b><font face="Arial, Helvetica, sans-serif" size="5" color="#FF0000">8.2 static hashing</font><i><font face="Arial, Helvetica, sans-serif" size="3" color="#CC0099"> /*杂凑*/</font></i><font face="Arial, Helvetica, sans-serif" size="4" color="#000000">
(1) <font color="#FF0000">hash table</font>
<font color="#0033CC">hash table ( ft )</font> ~ a fixed size table
<font color="#0033CC">hash function ( f (x) ) </font> ~ give the hash (home address ) of an
identifier, x, in the table.
<i><font color="#FF0000">hash table ( ft ) </font></i>is stored in sequential memory location that are
partitioned into b buckets <i>ht [0],..., ht [b -1]</i> . Each bucket has s
slots. <font color="#0033CC"> <i>T = B * S</i></font>
</font><font face="Arial, Helvetica, sans-serif" size="4" color="#FF33CC"><i><font size="3"> ex. X (length=6) 1 symbol +</font></i></font></b><font face="Arial, Helvetica, sans-serif" size="4" color="#FF33CC"><i><font size="3"><b> 5 digi</b><b>t or simbol T=<img src="image/sum.gif" width="144" height="34" align="top"></b>
</font></i></font><b><font face="Arial, Helvetica, sans-serif" size="4" color="#000000">
【<font color="#FF0000">definition</font>】The identifier density of a hash table is the ratio n/T,
where n is the number of identifier in the table. The loading density
or loading factor of a hash table is <img src="image/a.gif" width="15" height="12" align="middle"> = <i>n /(sb)</i>
<font color="#FF0000">synonyms</font> ~ if f (<i> i<font size="2">1</font></i> ) = f ( <i>i<font size="2">2 </font></i>) , then <i> i<font size="2">1</font></i> and <i>i<font size="2">2</font></i> are synonyms
with respect to f
<font color="#FF0000">overflow </font> ~ hash a new identifier, i , into a full bucket
<font color="#FF0000">collision </font> ~ hash two nonidentical identifiers into the same
bucket. (since the ratio<i> b/T </i> is usually small,we
cannot avoid collisions)
<font color="#FF0000">O( 1 ) </font> ~ time required to enter,delete, or search for
identifiers using hashing
</font></b></pre>
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