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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_714</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_713.html">< previous page</a></td> <td align="center" width="40%" style="background: #EEF3E2"><strong style="color: #2F4F4F; font-size: 120%;">page_714</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_715.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 714</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>Sum the Rows</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">Suppose we want to sum row number 3 (the fourth row) in array </font><font face="Courier New, Courier, Mono New, Courier, Mono" size="3">table</font><font face="Times New Roman, Times, Serif" size="3"> and print the result. We can do this easily with a For loop:</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">total聽=聽0;<br />for聽(col聽=聽0;聽col聽<聽NUM_COLS;聽col++)<br /><br />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total聽==聽table[3][0]聽+聽聽+聽table[3][col-1]<br />聽聽聽聽聽聽聽聽//聽&&聽0聽<=聽col聽<=聽NUM_COLS<br /><br />聽聽聽聽total聽=聽total聽+聽table[3][col];<br />cout聽<<聽Row聽sum:聽聽<<聽total聽<<聽endl;</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">This For loop runs through each column of </font><font face="Courier New, Courier, Mono New, Courier, Mono" size="3">table</font><font face="Times New Roman, Times, Serif" size="3">, while keeping the row index equal to 3. Every value in row 3 is added to </font><font face="Courier New, Courier, Mono New, Courier, Mono" size="3">total</font><font face="Times New Roman, Times, Serif" size="3">. Suppose we wanted to sum and print two rowsrow 2 and row 3. We could add a duplicate of the preceding code fragment, but with the index set to 2:</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">//聽Sum聽row聽2聽and聽print聽the聽sum<br /><br />total聽=聽0;<br />for聽(col聽=聽0;聽col聽<聽NUM_COLS;聽col++)<br /><br />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total聽==聽table[2][0]聽+聽聽+聽table[2][col-1]<br />聽聽聽聽聽聽聽聽//聽聽&&聽0聽<=聽col聽<=聽NUM_COLS<br /><br />聽聽聽聽total聽=聽total聽+聽table[2][col];<br />cout聽<<聽Row聽sum:聽聽<<聽total聽<<聽endl;<br /><br />//聽Sum聽row聽3聽and聽print聽the聽sum<br /><br />total聽=聽0;<br />for聽(col聽=聽0;聽col聽<聽NUM_COLS;聽col++)<br /><br />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total聽==聽table[3][0]聽+聽聽+聽table[3][col-1]<br />聽聽聽聽聽聽聽聽//聽&&聽0聽<=聽col聽<=聽NUM_COLS<br /><br />聽聽聽聽total聽=聽total聽+聽table[3][col];<br />cout聽<<聽Row聽sum:聽聽<<聽total聽<<聽endl;</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">or we could use a nested loop and make the row index a variable:</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_713.html">< previous page</a></td> <td align="center" width="40%" style="background: #EEF3E2"><strong style="color: #2F4F4F; font-size: 120%;">page_714</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_715.html">next page ></a></td> </tr> </table> </body> </html>⌨️ 快捷键说明
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