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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd"> <html> <head> <title>page_653</title> <link rel="stylesheet" href="reset.css" type="text/css" media="all"> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /> </head> <body> <table summary="top nav" border="0" width="100%"> <tr> <td align="left" width="30%" style="background: #EEF3E2"><a style="color: blue; font-size: 120%; font-weight: bold; text-decoration: none; font-family: verdana;" href="page_652.html">< previous page</a></td> <td align="center" width="40%" style="background: #EEF3E2"><strong style="color: #2F4F4F; font-size: 120%;">page_653</strong></td> <td align="right" width="30%" style="background: #EEF3E2"><a style="color: blue; font-size: 120%; font-weight: bold; text-decoration: none; font-family: verdana;" href="page_654.html">next page ></a></td> </tr> <tr> <td align="left" colspan="3" style="background: #ffffff; padding: 20px;"> <table border="0" width="100%" cellpadding="0"><tr><td align="center"> <table border="0" cellpadding="2" cellspacing="0" width="100%"><tr><td align="left"></td> <td align="right"></td> </tr></table></td></tr><tr><td align="left"><p></p><table border="0" cellspacing="0" cellpadding="0" width="100%"><tr><td align="right"><font face="Times New Roman, Times, Serif" size="2" color="#FF0000">Page 653</font></td></tr></table><table border="0" cellspacing="0" cellpadding="0"><tr><td rowspan="5"></td> <td colspan="3" height="12"></td> <td rowspan="5"></td></tr><tr><td colspan="3"></td></tr><tr><td></td> <td><font face="Courier New, Courier, Mono New, Courier, Mono" size="2">//聽Searches聽list聽for聽item,聽returning聽the聽index<br />//聽of聽item聽if聽item聽was聽found<br /><br />//聽Precondition:<br />//聽聽聽聽聽length聽<聽MAX_LENGTH<br />//聽聽&&聽list[0..length-1]聽are聽assigned聽&&聽item聽is聽assigned<br />//聽Postcondition:<br />//聽聽聽聽聽list聽is聽the聽same聽as聽list@entry聽except聽that聽list[length]聽is<br />//聽聽聽聽聽聽聽overwritten聽to聽aid聽in聽the聽search<br />//聽聽&&聽IF聽item聽is聽in聽list@entry<br />//聽聽聽聽聽聽聽聽聽found聽==聽TRUE聽&&聽list[index]聽==聽item<br />//聽聽聽聽聽ELSE<br />//聽聽聽聽聽聽聽聽聽found聽==聽FALSE聽&&聽index聽==聽length<br /><br />{<br />聽聽聽聽index聽=聽0;<br />聽聽聽聽list[length]聽=聽item;聽聽聽聽聽聽聽聽聽聽聽聽//聽Store聽item聽at聽position聽beyond<br />聽聽聽聽聽聽聽聽聽聽聽聽聽聽聽聽聽聽聽聽聽聽聽聽聽聽聽聽聽聽聽聽聽聽聽聽//聽end聽of聽list<br />聽聽聽聽while聽(item聽!=聽list[index])<br /><br />聽聽聽聽聽聽聽聽聽聽聽聽//聽Invariant聽(prior聽to聽test):<br />聽聽聽聽聽聽聽聽聽聽聽聽//聽聽聽聽聽item聽is聽not聽in聽list[0..index-1]<br /><br />聽聽聽聽聽聽聽聽index++;<br /><br />聽聽聽聽found聽=聽(index聽<聽length);<br />}</font></td><td></td></tr><tr><td colspan="3"></td></tr><tr><td colspan="3" height="1"></td></tr></table><table border="0" cellspacing="0" cellpadding="0"><tr><td rowspan="5"></td> <td colspan="3" height="12"></td> <td rowspan="5"></td></tr><tr><td colspan="3"></td></tr><tr><td></td> <td><font face="Times New Roman, Times, Serif" size="3"><i>Sorting</i></font></td><td></td></tr><tr><td colspan="3"></td></tr><tr><td colspan="3" height="1"></td></tr></table><table border="0" cellspacing="0" cellpadding="0"><tr><td rowspan="5"></td> <td colspan="3" height="12"></td> <td rowspan="5"></td></tr><tr><td colspan="3"></td></tr><tr><td></td> <td><font face="Times New Roman, Times, Serif" size="3">The </font><font face="Courier New, Courier, Mono New, Courier, Mono" size="3">Search</font><font face="Times New Roman, Times, Serif" size="3"> and </font><font face="Courier New, Courier, Mono New, Courier, Mono" size="3">Search2</font><font face="Times New Roman, Times, Serif" size="3"> algorithms both assume that the list to be searched is unordered. A drawback to searching an unordered list is that we must scan the entire list to discover that the search item is not there. Think what it would be like if your city telephone book contained people's names in random rather than alphabetical order. To look up Mary Anthony's phone number, you would have to start with the first name in the phone book and scan sequentially, page after page, until you found it. In the worst case, you might have to examine tens of thousands of names only to find out that Mary's name is not in the book.</font></td><td></td></tr><tr><td colspan="3"></td></tr><tr><td colspan="3" height="1"></td></tr></table><table border="0" cellspacing="0" cellpadding="0"><tr><td rowspan="5"></td> <td colspan="3" height="12"></td> <td rowspan="5"></td></tr><tr><td colspan="3"></td></tr><tr><td></td> <td><font face="Times New Roman, Times, Serif" size="3">Of course, telephone books <i>are</i> alphabetized, and the alphabetical ordering makes searching easier. If Mary Anthony's name is not in the book, you discover this fact quickly by starting with the A's and stopping the search as soon as you have passed the place where her name should be. In software development, arranging list items into order is a very common operation on lists. For example, we might want to put a list of stock numbers into either ascending or descending order, or we might want to put a list of words into alphabetical order. Arranging values into order is known as sorting.</font></td><td></td></tr><tr><td colspan="3"></td></tr><tr><td colspan="3" height="1"></td></tr></table></td></tr></table><p><font size="0"></font></p>聽 </td> </tr> <tr> <td align="left" width="30%" style="background: #EEF3E2"><a style="color: blue; font-size: 120%; font-weight: bold; text-decoration: none; font-family: verdana;" href="page_652.html">< previous page</a></td> <td align="center" width="40%" style="background: #EEF3E2"><strong style="color: #2F4F4F; font-size: 120%;">page_653</strong></td> <td align="right" width="30%" style="background: #EEF3E2"><a style="color: blue; font-size: 120%; font-weight: bold; text-decoration: none; font-family: verdana;" href="page_654.html">next page ></a></td> </tr> </table> </body> </html>⌨️ 快捷键说明
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