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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_659</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_658.html">< previous page</a></td> <td align="center" width="40%" style="background: #EEF3E2"><strong style="color: #2F4F4F; font-size: 120%;">page_659</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_660.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 659</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="Times New Roman, Times, Serif" size="3"><i>Inserting into an Ordered List</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">What if we want to add a new value to an already sorted list? We can store the new value at </font><font face="Courier New, Courier, Mono New, Courier, Mono" size="3">list[length]</font><font face="Times New Roman, Times, Serif" size="3">, increment </font><font face="Courier New, Courier, Mono New, Courier, Mono" size="3">length</font><font face="Times New Roman, Times, Serif" size="3">, and sort the array again. However, such a solution is <i>not</i> an efficient way of solving the problem. Inserting five new items results in five separate sorting operations. Let's build another list operation, named </font><font face="Courier New, Courier, Mono New, Courier, Mono" size="3">Insert</font><font face="Times New Roman, Times, Serif" size="3">, that inserts a value into a sorted list.</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">If we were to insert a value by hand into a sorted list, we would write the new value out to the side and draw a line showing where it belongs. We do so by scanning the list until we find a value greater than the one we are inserting. The new value goes in the list just before that point.</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">We can do something similar in our function. We can find the proper place in the list using the by-hand algorithm. Instead of writing the value to the side, we have to shift all the values larger than the new one down one place to make room for it. The main algorithm is expressed as follows, where </font><font face="Courier New, Courier, Mono New, Courier, Mono" size="3">item</font><font face="Times New Roman, Times, Serif" size="3"> is the value being inserted.</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="Courier New, Courier, Mono New, Courier, Mono" size="2">WHILE聽place聽not聽found聽AND聽more聽places聽to聽look<br />聽聽IF聽item聽>聽current聽component聽in聽list<br />聽聽聽聽聽increment聽current聽place<br />聽聽ELSE<br />聽聽聽聽place聽found<br />Shift聽remainder聽of聽list聽down<br />Insert聽item<br />increment聽length</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">Assuming that </font><font face="Courier New, Courier, Mono New, Courier, Mono" size="3">index</font><font face="Times New Roman, Times, Serif" size="3"> is the place where </font><font face="Courier New, Courier, Mono New, Courier, Mono" size="3">item</font><font face="Times New Roman, Times, Serif" size="3"> is to be inserted, the algorithm for Shift List Down is</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="Courier New, Courier, Mono New, Courier, Mono" size="2">Set聽list[length]聽聽聽=聽list[length-1]<br />Set聽list[length-1]聽=聽list[length-2]<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.<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.<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.<br />Set聽list[index+1]聽聽=聽list[index]</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">We can use a For loop that decrements the control variable to shift the components in the list down one position. We can code the modules Insert Item and Increment Length directly. This algorithm is illustrated in Figure 12-5. There is something familiar about the While loop in our algorithm: it is logically like the While loop in </font><font face="Courier New, Courier, Mono New, Courier, Mono" size="3">SearchOrd</font><font face="Times New Roman, Times, Serif" size="3">. In </font><font face="Courier New, Courier, Mono New, Courier, Mono" size="3">SearchOrd</font><font face="Times New Roman, Times, Serif" size="3">, we leave the loop either when we find </font><font face="Courier New, Courier, Mono New, Courier, Mono" size="3">item</font><font face="Times New Roman, Times, Serif" size="3"> or when we pass the place in the list where </font><font face="Courier New, Courier, Mono New, Courier, Mono" size="3">item</font><font face="Times New Roman, Times, Serif" size="3"> belongs.</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">We can simply use </font><font face="Courier New, Courier, Mono New, Courier, Mono" size="3">SearchOrd</font><font face="Times New Roman, Times, Serif" size="3"> to find the insertion place for us. On return from </font><font face="Courier New, Courier, Mono New, Courier, Mono" size="3">SearchOrd</font><font face="Times New Roman, Times, Serif" size="3">, if </font><font face="Courier New, Courier, Mono New, Courier, Mono" size="3">found</font><font face="Times New Roman, Times, Serif" size="3"> is </font><font face="Courier New, Courier, Mono New, Courier, Mono" size="3">FALSE</font><font face="Times New Roman, Times, Serif" size="3">, </font><font face="Courier New, Courier, Mono New, Courier, Mono" size="3">index</font><font face="Times New Roman, Times, Serif" size="3"> is the place in </font><font face="Courier New, Courier, Mono New, Courier, Mono" size="3">list</font><font face="Times New Roman, Times, Serif" size="3"> where </font><font face="Courier New, Courier, Mono New, Courier, Mono" size="3">item</font><font face="Times New Roman, Times, Serif" size="3"> should be inserted. If </font><font face="Courier New, Courier, Mono New, Courier, Mono" size="3">found</font><font face="Times New Roman, Times, Serif" size="3"> is </font><font face="Courier New, Courier, Mono New, Courier, Mono" size="3">TRUE</font><font face="Times New Roman, Times, Serif" size="3">, we can either insert a second copy or</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_658.html">< previous page</a></td> <td align="center" width="40%" style="background: #EEF3E2"><strong style="color: #2F4F4F; font-size: 120%;">page_659</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_660.html">next page ></a></td> </tr> </table> </body> </html>⌨️ 快捷键说明
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