leetcode-algorithms/src/DecodeTheMessage.java at master · anishLearnsToCode/leetcode-algorithms · GitHub

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// https://leetcode.com/problems/decode-the-message

// T: O(|key| + |message|)

// S: O(1)

import java.util.HashMap;

import java.util.Map;

public class DecodeTheMessage {

public String decodeMessage(String key, String message) {

final Map<Character, Character> mapping = getSubstitutionMap(key);

final StringBuilder result = new StringBuilder();

System.out.println(mapping);

for (int index = 0 ; index < message.length() ; index++) {

if (message.charAt(index) == ' ') {

result.append(' ');

} else {

result.append(mapping.get(message.charAt(index)));

}

return result.toString();

}

private Map<Character, Character> getSubstitutionMap(String key) {

final Map<Character, Character> result = new HashMap<>();

char letter = 'a';

for (int index = 0 ; index < key.length() ; index++) {

if (!result.containsKey(key.charAt(index)) && key.charAt(index) != ' ') {

result.put(key.charAt(index), letter++);

}

return result;

}

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