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Posted By

bcmoney on 06/07/12


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fibonacci Algorithms


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Fibonacci series (several different algorithms)

 / Published in: PHP
 

URL: http://bcmoney-mobiletv.com/blog/

Planning to add proper PHPunit and PHPlogger code examples and blog about it at http://bcmoney-mobiletv.com/blog/

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  1. <?php
  2.  
  3. /*************************************************
  4.  * Fibonacci Sequence
  5.  *   The original predictive algorithm. This is a 
  6.  *   compilation of several algorithms for computing
  7.  *   it in PHP5+.
  8.  *   More info on Fibonacci number: 
  9.  *   http://en.wikipedia.org/wiki/Fibonacci_number
  10.  * @author bcmoney 
  11.  * @author David Stockton
  12.  *************************************************/
  13.  
  14. /**
  15.  * Recursive
  16.  *   http://www.codewalkers.com/c/a/Miscellaneous/Recursion-in-PHP/2/#fkj8Lr7BcSAZCQQv.99
  17.  */
  18. function fibonacci_recursive ($n) {
  19.   if ($n == 1 || $n == 2) {
  20.     return 1;
  21.   }
  22.   else {
  23.     return fibonacci_recursive($n - 1)+fibonacci_recursive($n - 2);
  24.   }
  25. }
  26.  
  27.  
  28. /** 
  29.  * Iterative
  30.  *   http://www.codewalkers.com/c/a/Miscellaneous/Recursion-in-PHP/3/
  31.  * @author David Stockton 
  32.  */
  33. function fibonacci_iterative($num, $show_series="no") {
  34.   $retval = "";
  35.   if ($num == 1 ) {
  36.     return 1;
  37.   }
  38.   $num1=1;
  39.   $num2=0;
  40.   $retval = "1";
  41.  
  42.   for ($i = 1; $i &lt; $num; $i++) {
  43.     $fib = $num2 + $num1;
  44.     $num2 = $num1;
  45.     $num1=$fib;
  46.     if ($show_series == 'yes') {
  47.         $retval .= ", ".$fib;
  48.     }
  49.   }
  50.   if ($show_series == 'yes') {
  51.     return $retval;
  52.   } else {
  53.     return $fib;
  54.   }
  55. }
  56.  
  57.  
  58. /*************************************************/
  59. /* calculate, log and time each function */
  60. /*************************************************/
  61.   $time = microtime();
  62.   $time = explode(" ", $time);
  63.   $time1 = $time + $time[0];
  64. echo fibonacci_recursive(50, "yes");
  65.   $time = microtime();
  66.   $time = explode(" ", $time);
  67.   $time2 = $time[1] + $time[0];
  68. echo fibonacci_iterative(50, "yes");
  69.   $time = microtime();
  70.   $time = explode(" ", $time);
  71.   $time3 = $time[2] + $time[1] + $time[0];
  72.   $totaltime = ($time3 - $time2 - $time1);
  73.  
  74.   echo "Recursive: ".$time1."\n<br/>\n";
  75.   echo "Iterative: ".$time2."\n<br/>\n";
  76.   echo "Total runtime: ".$totaltime."\n<br/>\n";
  77. ?>

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