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<b><font face="Arial, Helvetica, sans-serif" size="4" color="#000000">③ <font color="#FF0000">Folding</font> <i><font size="3" color="#CC0099">/* 折叠法*/</font></i>
<font color="#0033CC"> method</font>
partition the identifier x into several part (same length except last
one), then add the parts together to obtain the hash address for x
<font color="#0033CC">add methods</font>
1. <i><font color="#FF0000">shift folding</font></i> <i><font size="3" color="#CC0099">/* 平移折叠*/</font></i>
shift all parts except the last one, so that the least significant bit
of each part lines up with the corresponding bit of the last part,
then add the parts together to obtain f(x)
〖<font color="#0033CC">example</font>〗
<font color="#FF0000">12320324111220 <font face="黑体" color="#000000"> ---> </font>123<font face="黑体" color="#000000">203</font>241<font face="黑体" color="#000000">112</font>20</font>
x is divided into the following parts:
x1 = 123, x2 = 203, x3 = 241, x4 = 112 , x5 = 20
hash address = 123 + 203 + 241 + 112 + 020 = 699
2. <i><font color="#FF0000">folding at the boundaries</font></i> <i><font size="3" color="#CC0099">/* 交叉反转*/</font></i>
reverses every other partition before adding
〖<font color="#0033CC">example</font>〗
<font color="#FF0000">12320324111220 <font face="黑体" color="#000000"> ---> </font>123<font face="黑体" color="#000000">203</font>241<font face="黑体" color="#000000">112</font>20</font>
x is divided into the following parts:
x1 = 123, x2 = <font color="#FF0000">203</font>, x3 = 241, x4 =<font color="#FF0000"> 112</font> , x5 = 20
hash address = 123 + <font color="#FF0000">302</font> + 241 + <font color="#FF0000">211</font> + 020 = 897
</font></b></pre>
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