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g2201_2300.s2227_encrypt_and_decrypt_strings.readme.md Maven / Gradle / Ivy

2227\. Encrypt and Decrypt Strings

Hard

You are given a character array `keys` containing **unique** characters and a string array `values` containing strings of length 2. You are also given another string array `dictionary` 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:

1.  For each character `c` in the string, we find the index `i` satisfying `keys[i] == c` in `keys`.
2.  Replace `c` with `values[i]` in the string.

Note that in case a character of the string is **not present** in `keys`, the encryption process cannot be carried out, and an empty string `""` is returned.

A string is **decrypted** with the following process:

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

Implement the `Encrypter` class:

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

**Example 1:**

**Input** ["Encrypter", "encrypt", "decrypt"] [[['a', 'b', 'c', 'd'], ["ei", "zf", "ei", "am"], ["abcd", "acbd", "adbc", "badc", "dacb", "cadb", "cbda", "abad"]], ["abcd"], ["eizfeiam"]]

**Output:** [null, "eizfeiam", 2]

**Explanation:** Encrypter encrypter = new Encrypter([['a', 'b', 'c', 'd'], ["ei", "zf", "ei", "am"], ["abcd", "acbd", "adbc", "badc", "dacb", "cadb", "cbda", "abad"]); 

encrypter.encrypt("abcd"); // return "eizfeiam". 
                            // 'a' maps to "ei", 'b' maps to "zf", 'c' maps to "ei", and 'd' maps to "am". 

encrypter.decrypt("eizfeiam"); // return 2. 
                                // "ei" can map to 'a' or 'c', "zf" maps to 'b', and "am" maps to 'd'. 
                                // Thus, the possible strings after decryption are "abad", "cbad", "abcd", and "cbcd". 
                                // 2 of those strings, "abad" and "abcd", appear in dictionary, so the answer is 2.

**Constraints:**

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