📄 6_2_1 哈希avl树的基本概念 - 《多任务下的数据结构与算法》 - 免费试读 - book_csdn_net.htm
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<H1><A href="http://book.csdn.net/bookfiles/65">多任务下的数据结构与算法 </A></H1>
<DIV style="FONT-SIZE: 15px; TEXT-ALIGN: center"><A
href="http://book.csdn.net/bookfiles/65/100652558.shtml">6.2.1 哈希AVL树的基本概念
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<H1 id=divCurrentNode
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href="http://book.csdn.net/bookfiles/65/100652558.shtml"><FONT color=red>6.2.1
哈希AVL树的基本概念</FONT></A></H1>
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<DIV style="FLOAT: left; WIDTH: 49%">·<A
href="http://book.csdn.net/bookfiles/65/100652555.shtml">5.1.3 树的遍历算法</A></DIV>
<DIV style="FLOAT: right; WIDTH: 49%">·<A
href="http://book.csdn.net/bookfiles/65/100652556.shtml">5.1.4 树的编码实现</A></DIV>
<DIV style="FLOAT: left; WIDTH: 49%">·<A
href="http://book.csdn.net/bookfiles/65/100652557.shtml">5.1.5
使用树的遍历算法来实现Xcopy功能</A></DIV>
<DIV style="FLOAT: right; WIDTH: 49%">·<A
href="http://book.csdn.net/bookfiles/65/100652559.shtml">6.2.2
哈希AVL树的查找</A></DIV>
<DIV style="FLOAT: left; WIDTH: 49%">·<A
href="http://book.csdn.net/bookfiles/65/100652560.shtml">6.2.3
哈希AVL树的插入</A></DIV>
<DIV style="FLOAT: right; WIDTH: 49%">·<A
href="http://book.csdn.net/bookfiles/65/100652561.shtml">6.2.4
哈希AVL树的删除</A></DIV></DIV></DIV></DIV>
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<H3 style="MARGIN-LEFT: 0cm; TEXT-INDENT: 0cm; LINE-HEIGHT: 16.4pt"><A
name=_Toc122884816></A><SPAN lang=EN-US>6.2.1</SPAN><SPAN lang=EN-US>
</SPAN><SPAN style="FONT-FAMILY: 方正准圆简体">哈希</SPAN><SPAN
lang=EN-US>AVL</SPAN><SPAN style="FONT-FAMILY: 方正准圆简体">树的基本概念</SPAN></H3>
<P class=MsoNormal style="LINE-HEIGHT: 16.4pt"><SPAN
style="FONT-FAMILY: 华康简宋">前面介绍了复合数据结构哈希红黑树，它避免了哈希表里数据无序及红黑树查找速度不足的缺点。在软件设计中，经常会追求设计更快的查找算法。像哈希表查找，一次就可以定位到数据，已经够快的了，但是哈希表对哈希函数的设计有很高要求，若哈希函数设计不好，理论上查找的最坏复杂度为</SPAN><SPAN
lang=EN-US>O(n)</SPAN><SPAN style="FONT-FAMILY: 宋体">；</SPAN><SPAN
style="FONT-FAMILY: 华康简宋">在二叉树中，查找速度较快的为</SPAN><SPAN lang=EN-US>AVL</SPAN><SPAN
style="FONT-FAMILY: 华康简宋">树，能不能将哈希表和</SPAN><SPAN lang=EN-US>AVL</SPAN><SPAN
style="FONT-FAMILY: 华康简宋">树结合起来，使得查找更快呢？</SPAN></P>
<P class=MsoNormal style="LINE-HEIGHT: 16.4pt"><SPAN
style="FONT-FAMILY: 华康简宋">本节就讨论另外一个复合数据结构</SPAN><SPAN
style="FONT-FAMILY: 华康简宋; LETTER-SPACING: -0.1pt">—</SPAN><SPAN
style="FONT-FAMILY: 华康简宋">—哈希</SPAN><SPAN lang=EN-US>AVL</SPAN><SPAN
style="FONT-FAMILY: 华康简宋">树。顾名思义，哈希</SPAN><SPAN lang=EN-US>AVL</SPAN><SPAN
style="FONT-FAMILY: 华康简宋">树是哈希表和</SPAN><SPAN lang=EN-US>AVL</SPAN><SPAN
style="FONT-FAMILY: 华康简宋">树的复合数据结构，那么哈希</SPAN><SPAN lang=EN-US>AVL</SPAN><SPAN
style="FONT-FAMILY: 华康简宋">树是不是也采用和哈希红黑树同样的复合方法呢？哈希</SPAN><SPAN
lang=EN-US>AVL</SPAN><SPAN
style="FONT-FAMILY: 华康简宋">树的每个节点是不是既有哈希表的特性，又有</SPAN><SPAN
lang=EN-US>AVL</SPAN><SPAN style="FONT-FAMILY: 华康简宋">树的特性呢？</SPAN></P>
<P class=MsoNormal style="LINE-HEIGHT: 16.3pt"><SPAN
style="FONT-FAMILY: 华康简宋">如果将哈希</SPAN><SPAN lang=EN-US>AVL</SPAN><SPAN
style="FONT-FAMILY: 华康简宋">树设计成类似哈希红黑树，通常</SPAN><SPAN lang=EN-US>AVL</SPAN><SPAN
style="FONT-FAMILY: 华康简宋">树比红黑树查找要快，但插入删除效率较低，哈希</SPAN><SPAN
lang=EN-US>AVL</SPAN><SPAN
style="FONT-FAMILY: 华康简宋">树可以采用哈希表的查找方法进行查找，</SPAN><SPAN
lang=EN-US>AVL</SPAN><SPAN
style="FONT-FAMILY: 华康简宋">树的查找方法在这里不起作用，因此，查找速度也就和哈希表一样，还不如直接使用哈希红黑树。要想查找更快，有必要换个思路来设计哈希</SPAN><SPAN
lang=EN-US>AVL</SPAN><SPAN style="FONT-FAMILY: 华康简宋">树。</SPAN></P>
<P class=MsoNormal style="LINE-HEIGHT: 16.3pt"><SPAN
style="FONT-FAMILY: 华康简宋">设计哈希</SPAN><SPAN lang=EN-US>AVL</SPAN><SPAN
style="FONT-FAMILY: 华康简宋">树的目的首先是要解决哈希表的缺点。哈希表的使用对哈希函数有很高要求，如果哈希函数设计不好可能有很多个数据具有相同的哈希值，而对这些相同哈希值的数据查找是采用顺序查找方式，效率非常低。如果对哈希表具有相同哈希值的数据不使用链式方法解决冲突，而采用</SPAN><SPAN
lang=EN-US>AVL</SPAN><SPAN
style="FONT-FAMILY: 华康简宋">树来解决冲突，那么对具有相同哈希值的数据的查找将变成</SPAN><SPAN
lang=EN-US>AVL</SPAN><SPAN
style="FONT-FAMILY: 华康简宋">树的查找，比链式的顺序查找效率将提高很多。</SPAN></P>
<P class=MsoNormal style="LINE-HEIGHT: 16.3pt"><SPAN
style="FONT-FAMILY: 华康简宋">哈希</SPAN><SPAN lang=EN-US>AVL</SPAN><SPAN
style="FONT-FAMILY: 华康简宋">树与哈希表的区别就是</SPAN><SPAN lang=EN-US>bucket</SPAN><SPAN
style="FONT-FAMILY: 华康简宋">中的指针是</SPAN><SPAN lang=EN-US>AVLTREE</SPAN><SPAN
style="FONT-FAMILY: 华康简宋">的节点类型，因此用</SPAN><SPAN lang=EN-US>C</SPAN><SPAN
style="FONT-FAMILY: 华康简宋">语言结构体来描述哈希</SPAN><SPAN lang=EN-US>AVL</SPAN><SPAN
style="FONT-FAMILY: 华康简宋">树如下。</SPAN></P>
<P class=4><SPAN lang=EN-US>typedef BINTREEBASENODE AVLTREENODE</SPAN><SPAN
style="FONT-FAMILY: 宋体">；</SPAN></P>
<P class=4><SPAN lang=EN-US>typedef struct HASHAVLTREE_st {</SPAN></P>
<P class=MsoNormal style="LINE-HEIGHT: 14pt"><SPAN lang=EN-US
style="FONT-SIZE: 9pt"> AVLTREENODE
**ppBucket</SPAN><SPAN style="FONT-SIZE: 9pt; FONT-FAMILY: 宋体">；</SPAN><SPAN
lang=EN-US style="FONT-SIZE: 9pt"> /* </SPAN><SPAN
style="FONT-SIZE: 9pt; FONT-FAMILY: 华康简宋">索引表指针</SPAN><SPAN lang=EN-US
style="FONT-SIZE: 9pt"> */</SPAN></P>
<P class=MsoNormal style="LINE-HEIGHT: 14pt"><SPAN lang=EN-US
style="FONT-SIZE: 9pt"> UINT
uBucketCount</SPAN><SPAN style="FONT-SIZE: 9pt; FONT-FAMILY: 宋体">；</SPAN><SPAN
lang=EN-US
style="FONT-SIZE: 9pt">
/* </SPAN><SPAN style="FONT-SIZE: 9pt; FONT-FAMILY: 华康简宋">索引表的大小</SPAN><SPAN
lang=EN-US style="FONT-SIZE: 9pt"> */</SPAN></P>
<P class=MsoNormal style="LINE-HEIGHT: 14pt"><SPAN lang=EN-US
style="FONT-SIZE: 9pt"> UINT
uNodeCount</SPAN><SPAN style="FONT-SIZE: 9pt; FONT-FAMILY: 宋体">；</SPAN><SPAN
lang=EN-US
style="FONT-SIZE: 9pt">
/* </SPAN><SPAN style="FONT-SIZE: 9pt; FONT-FAMILY: 华康简宋">表中实际节点的个数</SPAN><SPAN
lang=EN-US style="FONT-SIZE: 9pt"> */</SPAN></P>
<P class=MsoNormal style="LINE-HEIGHT: 14pt"><SPAN lang=EN-US
style="FONT-SIZE: 9pt"> UINT
uCurBucketNo</SPAN><SPAN style="FONT-SIZE: 9pt; FONT-FAMILY: 宋体">；</SPAN><SPAN
lang=EN-US
style="FONT-SIZE: 9pt">
/* </SPAN><SPAN style="FONT-SIZE: 9pt; FONT-FAMILY: 华康简宋">当前要执行的</SPAN><SPAN
lang=EN-US style="FONT-SIZE: 9pt">bucket</SPAN><SPAN
style="FONT-SIZE: 9pt; FONT-FAMILY: 华康简宋">序号</SPAN><SPAN lang=EN-US
style="FONT-SIZE: 9pt"> */</SPAN></P>
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