塞萨尔密码的PHP替代编码算法

问题描述：

您好，我在练习中将此练习作为测试的一部分，我该如何解决它或提示要解决它

hello i am stack with this exercise as part of a test, how can i solve it or hint to solve it

/**
 * Class SubstitutionEncodingAlgorithm
 */
class SubstitutionEncodingAlgorithm implements EncodingAlgorithm {

    /**
     * @var array
     */
    private $substitutions;

    /**
     * SubstitutionEncodingAlgorithm constructor.
     * @param $substitutions
     */
    public function __construct(array $substitutions) {
        $this->substitutions = array();
    }

    /**
     * Encodes text by substituting character with another one provided in the pair.
     * For example pair "ab" defines all "a" chars will be replaced with "b" and all "b" chars will be replaced with "a"
     * Examples:
     *      substitutions = ["ab"], input = "aabbcc", output = "bbaacc"
     *      substitutions = ["ab", "cd"], input = "adam", output = "bcbm"
     *
     * @param string $text
     * @return string
     */
    public function encode($text) {
        /**
         * @todo: Implement it
         */
    }

}

到目前为止，我已尝试在encode（）函数中进行了哪些操作，但仍无法正常工作，这是我做错了什么？

that what i ve tried so far in the encode () function but its not working, what i am doing wrong ?

public function encode($text) {
    $length = strlen($text);
            $newstr = '';
            for ($i = 0; $i < $length; $i++) {
                if (is_array($this->substitutions) && in_array(strtoupper($text[$i]), array_flip($this->substitutions)))
                    $newstr .= $this->substitutions[strtoupper($text[$i])];
            }


            return $newstr;
        }

我知道这是迄今为止要实施的cesar算法，对您有帮助

i understand that it is the cesar algorithm to be implemented so far, any help would be appreciated on how to do it

答

        $swapA = array();
        $swapB = array();
        $output = '';
        $aText = str_split($text);
        foreach($this->substitutions as $sub)
        {
            $swapA[] = substr($sub,0,1);
            $swapB[] = substr($sub,1,1);

        }

        foreach ($aText as $letter) {
            if (in_array(strtolower($letter, $swapA)) {
                $positionOccurence = array_search ($letter, $swapA);
                $replaced = $swapB[$positionOccurence];
                $output .= str_replace($letter, $replaced, $letter);
            } elseif (in_array(strtolower($letter), $swapB)) {
                $positionOccurence = array_search ($letter, $swapB);
                $replaced = $swapA[$positionOccurence];
                $output .= str_replace($letter, $replaced, $letter);
            } else {
                $output .= $letter;
            }
        }

        return $output;

塞萨尔密码的PHP替代编码算法

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