decode-the-message

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Algorithms

You are given the strings <code>key</code> and <code>message</code>, which represent a cipher key and a secret message, respectively. The steps to decode <code>message</code> are as follows:

<ol>
	<li>Use the first appearance of all 26 lowercase English letters in <code>key</code> as the order of the substitution table.</li>
	<li>Align the substitution table with the regular English alphabet.</li>
	<li>Each letter in <code>message</code> is then substituted using the table.</li>
	<li>Spaces <code>&#39; &#39;</code> are transformed to themselves.</li>
</ol>

<ul>
	<li>For example, given <code>key = &quot;happy boy&quot;</code> (actual key would have at least one instance of each letter in the alphabet), we have the partial substitution table of (<code>&#39;h&#39; -&gt; &#39;a&#39;</code>, <code>&#39;a&#39; -&gt; &#39;b&#39;</code>, <code>&#39;p&#39; -&gt; &#39;c&#39;</code>, <code>&#39;y&#39; -&gt; &#39;d&#39;</code>, <code>&#39;b&#39; -&gt; &#39;e&#39;</code>, <code>&#39;o&#39; -&gt; &#39;f&#39;</code>).</li>
</ul>

Return the decoded message.

&nbsp;
Example 1:
<img alt="" src="https://assets.leetcode.com/uploads/2022/05/08/ex1new4.jpg" style="width: 752px; height: 150px;" />
<pre>
Input: key = &quot;the quick brown fox jumps over the lazy dog&quot;, message = &quot;vkbs bs t suepuv&quot;
Output: &quot;this is a secret&quot;
Explanation: The diagram above shows the substitution table.
It is obtained by taking the first appearance of each letter in &quot;the quick brown fox jumps over the lazy dog&quot;.
</pre>

Example 2:
<img alt="" src="https://assets.leetcode.com/uploads/2022/05/08/ex2new.jpg" style="width: 754px; height: 150px;" />
<pre>
Input: key = &quot;eljuxhpwnyrdgtqkviszcfmabo&quot;, message = &quot;zwx hnfx lqantp mnoeius ycgk vcnjrdb&quot;
Output: &quot;the five boxing wizards jump quickly&quot;
Explanation: The diagram above shows the substitution table.
It is obtained by taking the first appearance of each letter in &quot;eljuxhpwnyrdgtqkviszcfmabo&quot;.
</pre>

&nbsp;
Constraints:

<ul>
	<li><code>26 &lt;= key.length &lt;= 2000</code></li>
	<li><code>key</code> consists of lowercase English letters and <code>&#39; &#39;</code>.</li>
	<li><code>key</code> contains every letter in the English alphabet (<code>&#39;a&#39;</code> to <code>&#39;z&#39;</code>) at least once.</li>
	<li><code>1 &lt;= message.length &lt;= 2000</code></li>
	<li><code>message</code> consists of lowercase English letters and <code>&#39; &#39;</code>.</li>
</ul>

decodeMessage

Decode the Message

Hash Table

String

给你字符串 <code>key</code> 和 <code>message</code> ，分别表示一个加密密钥和一段加密消息。解密 <code>message</code> 的步骤如下：

<ol>
	<li>使用 <code>key</code> 中 26 个英文小写字母第一次出现的顺序作为替换表中的字母 顺序 。</li>
	<li>将替换表与普通英文字母表对齐，形成对照表。</li>
	<li>按照对照表 替换 <code>message</code> 中的每个字母。</li>
	<li>空格 <code>' '</code> 保持不变。</li>
</ol>

<ul>
	<li>例如，<code>key = "happy boy"</code>（实际的加密密钥会包含字母表中每个字母 至少一次），据此，可以得到部分对照表（<code>'h' -&gt; 'a'</code>、<code>'a' -&gt; 'b'</code>、<code>'p' -&gt; 'c'</code>、<code>'y' -&gt; 'd'</code>、<code>'b' -&gt; 'e'</code>、<code>'o' -&gt; 'f'</code>）。</li>
</ul>

返回解密后的消息。

&nbsp;

示例 1：

<img alt="" src="https://assets.leetcode.com/uploads/2022/05/08/ex1new4.jpg" style="width: 752px; height: 150px;" />

<pre>
输入：key = "the quick brown fox jumps over the lazy dog", message = "vkbs bs t suepuv"
输出："this is a secret"
解释：对照表如上图所示。
提取 "the quick brown fox jumps over the lazy dog" 中每个字母的首次出现可以得到替换表。
</pre>

示例 2：

<img alt="" src="https://assets.leetcode.com/uploads/2022/05/08/ex2new.jpg" style="width: 754px; height: 150px;" />

<pre>
输入：key = "eljuxhpwnyrdgtqkviszcfmabo", message = "zwx hnfx lqantp mnoeius ycgk vcnjrdb"
输出："the five boxing wizards jump quickly"
解释：对照表如上图所示。
提取 "eljuxhpwnyrdgtqkviszcfmabo" 中每个字母的首次出现可以得到替换表。
</pre>

&nbsp;

提示：

<ul>
	<li><code>26 &lt;= key.length &lt;= 2000</code></li>
	<li><code>key</code> 由小写英文字母及 <code>' '</code> 组成</li>
	<li><code>key</code> 包含英文字母表中每个字符（<code>'a'</code> 到 <code>'z'</code>）至少一次</li>
	<li><code>1 &lt;= message.length &lt;= 2000</code></li>
	<li><code>message</code> 由小写英文字母和 <code>' '</code> 组成</li>
</ul>