Package g2201_2300.s2227_encrypt_and_decrypt_strings

Class Encrypter

  • public class Encrypter
extends Object
    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.

    • Constructor Detail

      • Encrypter

        public Encrypter​(char[] keys,
                 String[] values,
                 String[] dictionary)

    • Method Detail

      • decrypt

        public int decrypt​(String word2)