encrypt-and-decrypt-strings

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Algorithms

You are given a character array <code>keys</code> containing unique characters and a string array <code>values</code> containing strings of length 2. You are also given another string array <code>dictionary</code> that contains all permitted original strings after decryption. You should implement a data structure that can encrypt or decrypt a 0-indexed string.

A string is encrypted with the following process:

<ol>
	<li>For each character <code>c</code> in the string, we find the index <code>i</code> satisfying <code>keys[i] == c</code> in <code>keys</code>.</li>
	<li>Replace <code>c</code> with <code>values[i]</code> in the string.</li>
</ol>

Note that in case a character of the string is not present in <code>keys</code>, the encryption process cannot be carried out, and an empty string <code>&quot;&quot;</code> is returned.

A string is decrypted with the following process:

<ol>
	<li>For each substring <code>s</code> of length 2 occurring at an even index in the string, we find an <code>i</code> such that <code>values[i] == s</code>. If there are multiple valid <code>i</code>, we choose any one of them. This means a string could have multiple possible strings it can decrypt to.</li>
	<li>Replace <code>s</code> with <code>keys[i]</code> in the string.</li>
</ol>

Implement the <code>Encrypter</code> class:

<ul>
	<li><code>Encrypter(char[] keys, String[] values, String[] dictionary)</code> Initializes the <code>Encrypter</code> class with <code>keys, values</code>, and <code>dictionary</code>.</li>
	<li><code>String encrypt(String word1)</code> Encrypts <code>word1</code> with the encryption process described above and returns the encrypted string.</li>
	<li><code>int decrypt(String word2)</code> Returns the number of possible strings <code>word2</code> could decrypt to that also appear in <code>dictionary</code>.</li>
</ul>

&nbsp;
Example 1:

<pre>
Input
[&quot;Encrypter&quot;, &quot;encrypt&quot;, &quot;decrypt&quot;]
[[[&#39;a&#39;, &#39;b&#39;, &#39;c&#39;, &#39;d&#39;], [&quot;ei&quot;, &quot;zf&quot;, &quot;ei&quot;, &quot;am&quot;], [&quot;abcd&quot;, &quot;acbd&quot;, &quot;adbc&quot;, &quot;badc&quot;, &quot;dacb&quot;, &quot;cadb&quot;, &quot;cbda&quot;, &quot;abad&quot;]], [&quot;abcd&quot;], [&quot;eizfeiam&quot;]]
Output
[null, &quot;eizfeiam&quot;, 2]

Explanation
Encrypter encrypter = new Encrypter([[&#39;a&#39;, &#39;b&#39;, &#39;c&#39;, &#39;d&#39;], [&quot;ei&quot;, &quot;zf&quot;, &quot;ei&quot;, &quot;am&quot;], [&quot;abcd&quot;, &quot;acbd&quot;, &quot;adbc&quot;, &quot;badc&quot;, &quot;dacb&quot;, &quot;cadb&quot;, &quot;cbda&quot;, &quot;abad&quot;]);
encrypter.encrypt(&quot;abcd&quot;); // return &quot;eizfeiam&quot;. 
&nbsp; // &#39;a&#39; maps to &quot;ei&quot;, &#39;b&#39; maps to &quot;zf&quot;, &#39;c&#39; maps to &quot;ei&quot;, and &#39;d&#39; maps to &quot;am&quot;.
encrypter.decrypt(&quot;eizfeiam&quot;); // return 2. 
 // &quot;ei&quot; can map to &#39;a&#39; or &#39;c&#39;, &quot;zf&quot; maps to &#39;b&#39;, and &quot;am&quot; maps to &#39;d&#39;. 
 // Thus, the possible strings after decryption are &quot;abad&quot;, &quot;cbad&quot;, &quot;abcd&quot;, and &quot;cbcd&quot;. 
 // 2 of those strings, &quot;abad&quot; and &quot;abcd&quot;, appear in dictionary, so the answer is 2.
</pre>

&nbsp;
Constraints:

<ul>
	<li><code>1 &lt;= keys.length == values.length &lt;= 26</code></li>
	<li><code>values[i].length == 2</code></li>
	<li><code>1 &lt;= dictionary.length &lt;= 100</code></li>
	<li><code>1 &lt;= dictionary[i].length &lt;= 100</code></li>
	<li>All <code>keys[i]</code> and <code>dictionary[i]</code> are unique.</li>
	<li><code>1 &lt;= word1.length &lt;= 2000</code></li>
	<li><code>2 &lt;= word2.length &lt;= 200</code></li>
	<li>All <code>word1[i]</code> appear in <code>keys</code>.</li>
	<li><code>word2.length</code> is even.</li>
	<li><code>keys</code>, <code>values[i]</code>, <code>dictionary[i]</code>, <code>word1</code>, and <code>word2</code> only contain lowercase English letters.</li>
	<li>At most <code>200</code> calls will be made to <code>encrypt</code> and <code>decrypt</code> in total.</li>
</ul>

Encrypt and Decrypt Strings

Implement Trie (Prefix Tree)

implement-trie-prefix-tree

实现 Trie (前缀树)

Word Search II

word-search-ii

单词搜索 II

Implement Trie II (Prefix Tree)

implement-trie-ii-prefix-tree

实现 Trie （前缀树） II

Find the Sum of Encrypted Integers

find-the-sum-of-encrypted-integers

求出加密整数的和

Design

Trie

Array

Hash Table

String

给你一个字符数组 <code>keys</code> ，由若干 互不相同 的字符组成。还有一个字符串数组 <code>values</code> ，内含若干长度为 2 的字符串。另给你一个字符串数组 <code>dictionary</code> ，包含解密后所有允许的原字符串。请你设计并实现一个支持加密及解密下标从 0 开始字符串的数据结构。

字符串 加密 按下述步骤进行：

<ol>
	<li>对字符串中的每个字符 <code>c</code> ，先从 <code>keys</code> 中找出满足 <code>keys[i] == c</code> 的下标 <code>i</code> 。</li>
	<li>在字符串中，用&nbsp;<code>values[i]</code> 替换字符 <code>c</code> 。</li>
</ol>

请注意，如果&nbsp;<code>keys</code> 中不存在字符串中的字符，则无法执行加密过程，返回空字符串 <code>""</code>。

字符串 解密 按下述步骤进行：

<ol>
	<li>将字符串每相邻 2 个字符划分为一个子字符串，对于每个子字符串 <code>s</code> ，找出满足 <code>values[i] == s</code> 的一个下标 <code>i</code> 。如果存在多个有效的 <code>i</code> ，从中选择 任意 一个。这意味着一个字符串解密可能得到多个解密字符串。</li>
	<li>在字符串中，用 <code>keys[i]</code> 替换 <code>s</code> 。</li>
</ol>

实现 <code>Encrypter</code> 类：

<ul>
	<li><code>Encrypter(char[] keys, String[] values, String[] dictionary)</code> 用 <code>keys</code>、<code>values</code> 和 <code>dictionary</code> 初始化 <code>Encrypter</code> 类。</li>
	<li><code>String encrypt(String word1)</code> 按上述加密过程完成对 <code>word1</code> 的加密，并返回加密后的字符串。</li>
	<li><code>int decrypt(String word2)</code> 统计并返回可以由 <code>word2</code> 解密得到且出现在 <code>dictionary</code> 中的字符串数目。</li>
</ul>

&nbsp;

示例：

<pre>
输入：
["Encrypter", "encrypt", "decrypt"]
[[['a', 'b', 'c', 'd'], ["ei", "zf", "ei", "am"], ["abcd", "acbd", "adbc", "badc", "dacb", "cadb", "cbda", "abad"]], ["abcd"], ["eizfeiam"]]
输出：
[null, "eizfeiam", 2]

解释：
Encrypter encrypter = new Encrypter([['a', 'b', 'c', 'd'], ["ei", "zf", "ei", "am"], ["abcd", "acbd", "adbc", "badc", "dacb", "cadb", "cbda", "abad"]);
encrypter.encrypt("abcd"); // 返回 "eizfeiam"。 
&nbsp; // 'a' 映射为 "ei"，'b' 映射为 "zf"，'c' 映射为 "ei"，'d' 映射为 "am"。
encrypter.decrypt("eizfeiam"); // return 2. 
 // "ei" 可以映射为 'a' 或 'c'，"zf" 映射为 'b'，"am" 映射为 'd'。 
 // 因此，解密后可以得到的字符串是 "abad"，"cbad"，"abcd" 和 "cbcd"。 
 // 其中 2 个字符串，"abad" 和 "abcd"，在 dictionary 中出现，所以答案是 2 。
</pre>

&nbsp;

提示：

<ul>
	<li><code>1 &lt;= keys.length == values.length &lt;= 26</code></li>
	<li><code>values[i].length == 2</code></li>
	<li><code>1 &lt;= dictionary.length &lt;= 100</code></li>
	<li><code>1 &lt;= dictionary[i].length &lt;= 100</code></li>
	<li>所有 <code>keys[i]</code> 和 <code>dictionary[i]</code> 互不相同</li>
	<li><code>1 &lt;= word1.length &lt;= 2000</code></li>
	<li><code>1 &lt;= word2.length &lt;= 200</code></li>
	<li>所有 <code>word1[i]</code> 都出现在 <code>keys</code> 中</li>
	<li><code>word2.length</code> 是偶数</li>
	<li><code>keys</code>、<code>values[i]</code>、<code>dictionary[i]</code>、<code>word1</code> 和 <code>word2</code> 只含小写英文字母</li>
	<li>至多调用 <code>encrypt</code> 和 <code>decrypt</code> 总计 <code>200</code> 次</li>
</ul>