Practice Encrypt and Decrypt Strings

Read the task, work through the examples, and check your approach against the constraints. Use the original LeetCode task for coding and submissions.

Hard#2227

LeetCode Problem

Encrypt and Decrypt Strings

Array Hash Table String Design Trie

Problem Statement

Encrypter(keys,values,dictionary) maps each distinct key character to a two-letter string; values may repeat. encrypt(word1) concatenates mappings, returning an empty string if a character has no mapping. decrypt(word2) counts distinct dictionary words whose encryption equals word2. It does not count all theoretically possible plaintext strings. Practice approach: Build the character map and pre-encrypt every dictionary word that can be encoded. Count identical ciphertexts in a frequency map, making decryption a lookup. This avoids exponential branching when several keys share a code. Test code collisions and dictionary entries containing unmapped characters.

Source: Encrypt and Decrypt Strings on LeetCode. Use the original task for its coding environment and submissions.

Examples

# Example 1

Input

["Encrypter","encrypt","decrypt","decrypt"]
[[["a","b","c"],["xy","zz","xy"],["ab","cb","aa","d"]],["ab"],["xyzz"],["zzxy"]]

Output

[null,"xyzz",2,0]

Explanation

ab and cb both encrypt to xyzz. No dictionary entry encrypts to zzxy; d cannot be encoded.

Constraints

1 <= keys.length == values.length <= 26; each value has length 2.

1 <= dictionary.length <= 100; word lengths are 1 to 100.

Keys and dictionary entries are distinct; all text is lowercase.

1 <= word1.length <= 2000; generated word1 characters have mappings.

2 <= word2.length <= 200 and is even.

At most 200 total calls.

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