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:
Use the first appearance of all 26 lowercase English letters in
key
as the order of the substitution table.Align the substitution table with the regular English alphabet.
Each letter in
message
is then substituted using the table.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.
LeetCode Problem - 2325
import java.util.*;
class Solution {
// Method to decode a message using a given key
public String decodeMessage(String key, String message) {
// Removing spaces from the key
String keyWithoutSpace = key.replaceAll("\\s+","");
// Creating a map to store the key-value pairs
Map<Character, Character> hm = new HashMap<>();
// Assigning values to characters in the key
char value = 'a';
for (int i = 0; i < keyWithoutSpace.length(); i++) {
if (!hm.containsKey(keyWithoutSpace.charAt(i))) {
hm.put(keyWithoutSpace.charAt(i), value);
value++;
}
}
// Splitting the message into words
String[] msgArr = message.split(" ");
List<String> list = new ArrayList<>();
// Decoding each word in the message
for (String string : msgArr) {
StringBuilder sb = new StringBuilder();
for (int j = 0; j < string.length(); j++) {
sb.append(hm.get(string.charAt(j)));
}
list.add(sb.toString());
}
// Constructing the decoded message
StringBuilder ans = new StringBuilder(String.join(" ", list));
// Adding necessary spaces to match the length of the original message
if (ans.length() != message.length()) {
int diff = message.length() - ans.length();
ans.append(" ".repeat(Math.max(0, diff)));
}
// Returning the decoded message
return ans.toString();
}
}