贪婪算法.htm

数据挖掘常用的贪婪算法

style="FONT-SIZE: 10pt; COLOR: black; FONT-FAMILY: 仿宋_GB2312; mso-font-kerning: 0pt">。任何满足限制条件的一组实数</SPAN><I><SPAN 
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style="FONT-SIZE: 10pt; COLOR: black; mso-font-kerning: 0pt; mso-fareast-font-family: 仿宋_GB2312">x</SPAN></I><I><SPAN 
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</SPAN></I><SPAN 
style="FONT-SIZE: 10pt; COLOR: black; FONT-FAMILY: 仿宋_GB2312; mso-font-kerning: 0pt">都是可行解，而使</SPAN><I><SPAN 
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style="FONT-SIZE: 5pt; COLOR: black; mso-font-kerning: 0pt; mso-fareast-font-family: 仿宋_GB2312">= 
1</SPAN><I><SPAN lang=EN-US 
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</SPAN></I><I><SPAN lang=EN-US 
style="FONT-SIZE: 10pt; COLOR: black; mso-font-kerning: 0pt; mso-fareast-font-family: 仿宋_GB2312">x</SPAN></I><I><SPAN 
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</SPAN></I><SPAN 
style="FONT-SIZE: 10pt; COLOR: black; FONT-FAMILY: 仿宋_GB2312; mso-font-kerning: 0pt">最大的可行解是最优解。<SPAN 
lang=EN-US><o:p></o:p></SPAN></SPAN></P>
<P class=MsoNormal 
style="TEXT-INDENT: 20.1pt; TEXT-ALIGN: left; mso-char-indent-count: 2.0; mso-char-indent-size: 10.05pt; mso-layout-grid-align: none" 
align=left><B><SPAN 
style="FONT-SIZE: 10pt; COLOR: black; FONT-FAMILY: 仿宋_GB2312; mso-font-kerning: 0pt">例</SPAN></B><B><SPAN 
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[</SPAN></B><B><SPAN 
style="FONT-SIZE: 10pt; COLOR: black; FONT-FAMILY: 仿宋_GB2312; mso-font-kerning: 0pt">装载问题</SPAN></B><B><SPAN 
lang=EN-US 
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</SPAN></B><SPAN lang=EN-US 
style="FONT-SIZE: 10pt; COLOR: black; FONT-FAMILY: 仿宋_GB2312; mso-font-kerning: 0pt"><SPAN 
style="mso-spacerun: yes">&nbsp;</SPAN>有一艘大船准备用来装载货物。所有待装货物都装在货箱中且所有货箱的大小都一样，但货箱的重量都各不相同。设第</SPAN><I><SPAN 
lang=EN-US 
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</SPAN></I><SPAN 
style="FONT-SIZE: 10pt; COLOR: black; FONT-FAMILY: 仿宋_GB2312; mso-font-kerning: 0pt">个货箱的重量为</SPAN><I><SPAN 
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style="FONT-SIZE: 10pt; COLOR: black; FONT-FAMILY: 仿宋_GB2312; mso-font-kerning: 0pt">（</SPAN><SPAN 
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style="FONT-SIZE: 10pt; COLOR: black; mso-font-kerning: 0pt; mso-fareast-font-family: 仿宋_GB2312">1</SPAN><SPAN 
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style="FONT-SIZE: 10pt; COLOR: black; FONT-FAMILY: 仿宋_GB2312; mso-font-kerning: 0pt">≤</SPAN><I><SPAN 
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style="FONT-SIZE: 10pt; COLOR: black; mso-font-kerning: 0pt; mso-fareast-font-family: 仿宋_GB2312">n</SPAN></I><SPAN 
style="FONT-SIZE: 10pt; COLOR: black; FONT-FAMILY: 仿宋_GB2312; mso-font-kerning: 0pt">），而货船的最大载重量为</SPAN><I><SPAN 
lang=EN-US 
style="FONT-SIZE: 10pt; COLOR: black; mso-font-kerning: 0pt; mso-fareast-font-family: 仿宋_GB2312">c</SPAN></I><SPAN 
style="FONT-SIZE: 10pt; COLOR: black; FONT-FAMILY: 仿宋_GB2312; mso-font-kerning: 0pt">，我们的目的是在货船上装入最多的货物。<SPAN 
lang=EN-US><o:p></o:p></SPAN></SPAN></P>
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style="TEXT-INDENT: 20pt; TEXT-ALIGN: left; mso-char-indent-count: 2.0; mso-char-indent-size: 10.0pt; mso-layout-grid-align: none" 
align=left><SPAN 
style="FONT-SIZE: 10pt; COLOR: black; FONT-FAMILY: 仿宋_GB2312; mso-font-kerning: 0pt">这个问题可以作为最优化问题进行描述：设存在一组变量</SPAN><I><SPAN 
lang=EN-US 
style="FONT-SIZE: 10pt; COLOR: black; mso-font-kerning: 0pt; mso-fareast-font-family: 仿宋_GB2312">x</SPAN></I><I><SPAN 
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</SPAN></I><SPAN 
style="FONT-SIZE: 10pt; COLOR: black; FONT-FAMILY: 仿宋_GB2312; mso-font-kerning: 0pt">，其可能取值为</SPAN><SPAN 
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style="FONT-SIZE: 10pt; COLOR: black; FONT-FAMILY: 仿宋_GB2312; mso-font-kerning: 0pt">或</SPAN><SPAN 
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style="FONT-SIZE: 10pt; COLOR: black; mso-font-kerning: 0pt; mso-fareast-font-family: 仿宋_GB2312">1</SPAN><SPAN 
style="FONT-SIZE: 10pt; COLOR: black; FONT-FAMILY: 仿宋_GB2312; mso-font-kerning: 0pt">。如</SPAN><I><SPAN 
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</SPAN></I><SPAN 
style="FONT-SIZE: 10pt; COLOR: black; FONT-FAMILY: 仿宋_GB2312; mso-font-kerning: 0pt">为</SPAN><SPAN 
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style="FONT-SIZE: 10pt; COLOR: black; mso-font-kerning: 0pt; mso-fareast-font-family: 仿宋_GB2312">0</SPAN><SPAN 
style="FONT-SIZE: 10pt; COLOR: black; FONT-FAMILY: 仿宋_GB2312; mso-font-kerning: 0pt">，则货箱</SPAN><I><SPAN 
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</SPAN></I><SPAN 
style="FONT-SIZE: 10pt; COLOR: black; FONT-FAMILY: 仿宋_GB2312; mso-font-kerning: 0pt">将不被装上船；如</SPAN><I><SPAN 
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lang=EN-US 
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</SPAN></I><SPAN 
style="FONT-SIZE: 10pt; COLOR: black; FONT-FAMILY: 仿宋_GB2312; mso-font-kerning: 0pt">为</SPAN><SPAN 
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style="FONT-SIZE: 10pt; COLOR: black; FONT-FAMILY: 仿宋_GB2312; mso-font-kerning: 0pt">，则货箱</SPAN><I><SPAN 
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</SPAN></I><SPAN 
style="FONT-SIZE: 10pt; COLOR: black; FONT-FAMILY: 仿宋_GB2312; mso-font-kerning: 0pt">将被装上船。我们的目的是找到一组</SPAN><I><SPAN 
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</SPAN></I><SPAN 
style="FONT-SIZE: 10pt; COLOR: black; FONT-FAMILY: 仿宋_GB2312; mso-font-kerning: 0pt">，使它满足限制条件</SPAN><I><SPAN 
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style="FONT-SIZE: 10pt; COLOR: black; mso-font-kerning: 0pt; mso-fareast-font-family: 仿宋_GB2312">x</SPAN></I><I><SPAN 
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</SPAN><SPAN lang=EN-US 
style="FONT-SIZE: 10pt; COLOR: black; mso-font-kerning: 0pt; mso-fareast-font-family: 仿宋_GB2312">{0, 
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style="FONT-SIZE: 10pt; COLOR: black; FONT-FAMILY: 仿宋_GB2312; mso-font-kerning: 0pt">。相应的优化函数是</SPAN><I><SPAN 
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1</SPAN><I><SPAN lang=EN-US 
style="FONT-SIZE: 10pt; COLOR: black; mso-font-kerning: 0pt; mso-fareast-font-family: 仿宋_GB2312">x</SPAN></I><I><SPAN 
lang=EN-US 
style="FONT-SIZE: 5pt; COLOR: black; mso-font-kerning: 0pt; mso-fareast-font-family: 仿宋_GB2312">i 
</SPAN></I><SPAN 
style="FONT-SIZE: 10pt; COLOR: black; FONT-FAMILY: 仿宋_GB2312; mso-font-kerning: 0pt">。<SPAN 
lang=EN-US><o:p></o:p></SPAN></SPAN></P>
<P class=MsoNormal 
style="TEXT-INDENT: 20pt; TEXT-ALIGN: left; mso-char-indent-count: 2.0; mso-char-indent-size: 10.0pt; mso-layout-grid-align: none" 
align=left><SPAN 
style="FONT-SIZE: 10pt; COLOR: black; FONT-FAMILY: 仿宋_GB2312; mso-font-kerning: 0pt">满足限制条件的每一组</SPAN><I><SPAN 
lang=EN-US 
style="FONT-SIZE: 10pt; COLOR: black; mso-font-kerning: 0pt; mso-fareast-font-family: 仿宋_GB2312">x</SPAN></I><I><SPAN 
lang=EN-US 
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</SPAN></I><SPAN 
style="FONT-SIZE: 10pt; COLOR: black; FONT-FAMILY: 仿宋_GB2312; mso-font-kerning: 0pt">都是一个可行解，能使</SPAN><I><SPAN 
lang=EN-US 
style="FONT-SIZE: 5pt; COLOR: black; mso-font-kerning: 0pt; mso-fareast-font-family: 仿宋_GB2312">n 
</SPAN></I><SPAN lang=EN-US 
style="FONT-SIZE: 10pt; COLOR: black; FONT-FAMILY: Symbol; mso-font-kerning: 0pt; mso-fareast-font-family: 仿宋_GB2312">&aring;</SPAN><I><SPAN 
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style="FONT-SIZE: 5pt; COLOR: black; mso-font-kerning: 0pt; mso-fareast-font-family: 仿宋_GB2312">i</SPAN></I><SPAN 
lang=EN-US 
style="FONT-SIZE: 5pt; COLOR: black; mso-font-kerning: 0pt; mso-fareast-font-family: 仿宋_GB2312">= 
1</SPAN><I><SPAN lang=EN-US 
style="FONT-SIZE: 10pt; COLOR: black; mso-font-kerning: 0pt; mso-fareast-font-family: 仿宋_GB2312">x</SPAN></I><I><SPAN 
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style="FONT-SIZE: 5pt; COLOR: black; mso-font-kerning: 0pt; mso-fareast-font-family: 仿宋_GB2312">i 
</SPAN></I><SPAN 
style="FONT-SIZE: 10pt; COLOR: black; FONT-FAMILY: 仿宋_GB2312; mso-font-kerning: 0pt">取得最大值的方案是最优解。<SPAN 
lang=EN-US><o:p></o:p></SPAN></SPAN></P>
<P class=MsoNormal 
style="TEXT-INDENT: 20.1pt; TEXT-ALIGN: left; mso-char-indent-count: 2.0; mso-char-indent-size: 10.05pt; mso-layout-grid-align: none" 
align=left><B><SPAN 
style="FONT-SIZE: 10pt; COLOR: black; FONT-FAMILY: 仿宋_GB2312; mso-font-kerning: 0pt">例</SPAN></B><B><SPAN 
lang=EN-US 
style="FONT-SIZE: 10pt; COLOR: black; FONT-FAMILY: Arial; mso-font-kerning: 0pt; mso-fareast-font-family: 仿宋_GB2312">1-3