# Thread: [RESOLVED] Algo needed: Spiral of numbers based on _n_

1. Registered User
Join Date
Nov 2006
Location
Ekenäs, Finland
Posts
17

## [RESOLVED] Algo needed: Spiral of numbers based on _n_

Hi,
I'm trying to solve this one assignment we have in PHP.

Based on the given number n, the script is supposed to print out a n*n grid of numbers following the pattern in this image:
http://img222.imageshack.us/img222/4623/79890400.png

In this example the given number n is 4.

Would any of you have an idea for a good algorithm?

2. I couldn't come up with a "good" algorithm, just a more-or-less brute force approach:
PHP Code:
``` <?php function spiral(\$n) {    \$n = abs((int)\$n);    \$result = array();    \$count = 0;    for(\$i = 1; \$i <= \$n; \$i++) {       if(\$i % 2) {          for(\$y = \$i, \$x = 1; \$x <= \$i; \$x++) {             \$result[\$x][\$y] = ++\$count;          }          for(\$x = \$i, \$y = \$i - 1; \$y >= 1; \$y--) {             \$result[\$x][\$y] = ++\$count;          }       }       else {          for(\$y = 1, \$x = \$i; \$y <= \$i; \$y++) {             \$result[\$x][\$y] = ++\$count;          }          for(\$x = \$i - 1, \$y = \$i; \$x >= 1; \$x--) {             \$result[\$x][\$y] = ++\$count;          }       }    }    return \$result; } ?> <html><head><title>Test</title> <style type='text/css'> table {    border-collapse: collapse;    border: solid 2px black; } td {    text-align: center;    padding: 0.2em;    border: solid 1px black; } </style></head><body> <?php \$test = range(1,6); foreach(\$test as \$num) {    echo "<h3>Test Value: \$num</h3>\n";    \$data = spiral(\$num);    echo "<table>\n";    for(\$y = 1; \$y <= \$num; \$y++) {       echo "<tr>";       for(\$x = 1; \$x <= \$num; \$x++) {          echo "<td>".\$data[\$x][\$y]."</td>";       }       echo "</tr>\n";    }    echo "<table>\n"; } ?> </body></html> ```

3. Registered User
Join Date
Nov 2006
Location
Ekenäs, Finland
Posts
17
Thank you NogDog, the solution is Perfect!!
Great job!

Happy holidays!

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