用PHP迭代器來實現一個費伯納西數列

標籤：費伯納西數列   php迭代器   

費伯納西數列通常做法是用遞迴實現，當然還有其它的方法。這裡現學現賣，用PHP的迭代器來實現一個費伯納西數列，幾乎沒有什麼難度，只是把類裡的next()方法重寫了一次。注釋已經寫到代碼中，也是相當好理解的。

<?php/**@author [email protected]*/class Fibonacci implements Iterator {     private $previous = 1;     private $current = 0;     private $key = 0;         public function current() {         return $this->current;     }         public function key() {         return $this->key;     }         public function next() { // 關鍵在這裡// 將當前值儲存到  $newprevious        $newprevious = $this->current; // 將上一個值與當前值的和賦給當前值        $this->current += $this->previous; // 前一個當前值賦給上一個值        $this->previous = $newprevious;         $this->key++;     }         public function rewind() {         $this->previous = 1;         $this->current = 0;         $this->key = 0;     }         public function valid() {         return true;     } } $seq = new Fibonacci; $i = 0; foreach ($seq as $f) {     echo "$f ";     if ($i++ === 15) break; } ?>

程式運行結果：

0 1 1 2 3 5 8 13 21 34 55 89 144 233 377 610