LeetCode 2325. Decode the Message

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

1. Use the first appearance of all 26 lowercase English letters in key as the order of the substitution table.

2. Align the substitution table with the regular English alphabet.

3. Each letter in message is then substituted using the table.

4. Spaces ' ' are transformed to themselves.

• For example, given key = "happy boy" (actual key would have at least one instance of each letter in the alphabet), we have the partial substitution table of ('h' -> 'a', 'a' -> 'b', 'p' -> 'c', 'y' -> 'd', 'b' -> 'e', 'o' -> 'f').

Return the decoded message.

Example 1:

Input: key = "the quick brown fox jumps over the lazy dog", 

message = "vkbs bs t suepuv"

Output: "this is a secret"

Explanation: The diagram above shows the substitution table. It is obtained by taking the first appearance of each letter in "the quick brown fox jumps over the lazy dog".

Example 2:

Input: key = "eljuxhpwnyrdgtqkviszcfmabo", 

message = "zwx hnfx lqantp mnoeius ycgk vcnjrdb"

Output: "the five boxing wizards jump quickly"

Explanation: 

The diagram above shows the substitution table. It is obtained by taking the first appearance of each letter in "eljuxhpwnyrdgtqkviszcfmabo".

Constraints:

• 26 <= key.length <= 2000

• key consists of lowercase English letters and ' '.

• key contains every letter in the English alphabet ('a' to 'z') at least once.

• 1 <= message.length <= 2000

• message consists of lowercase English letters and ' '.

• 题目是easy题目，其实就是做一个映射，然后根据message 返回映射的信息即可；

• 用hashmap可以，也可以直接用数组；下面是代码：

Runtime: 7 ms, faster than 71.47% of Java online submissions for Decode the Message.

Memory Usage: 42.7 MB, less than 50.31% of Java online submissions for Decode the Message.