src/main/java/com/fishercoder/solutions/_2325.java

package com.fishercoder.solutions;

import java.util.HashMap;
import java.util.Map;

public class _2325 {
    public static class Solution1 {
        public String decodeMessage(String key, String message) {
            Map<Character, Character> map = new HashMap<>();
            char realChar = 'a';
            for (char c : key.toCharArray()) {
                if (c == ' ') {
                    continue;
                }
                if (!map.containsKey(c)) {
                    map.put(c, realChar);
                    realChar++;
                }
                if (map.size() >= 26) {
                    break;
                }
            }
            StringBuilder sb = new StringBuilder();
            for (char c : message.toCharArray()) {
                if (c == ' ') {
                    sb.append(' ');
                } else {
                    sb.append(map.get(c));
                }
            }
            return sb.toString();
        }
    }

    public static class Solution2 {

        public String decodeMessage(String key, String message) {
            // put first occurrence of each char of key in hashmap, where <k,v> k = char in key, v = incremental a - z alphabets

            Map<Character, Character> bucket = new HashMap<>();
            char ch = 'a';
            char[] keyArr = key.toCharArray();
            StringBuilder result = new StringBuilder();

            for (int i = 0; i < keyArr.length; i++) {
                if (keyArr[i] != ' ' && !bucket.containsKey(keyArr[i])) {
                    bucket.put(keyArr[i], ch++);
                }
            }

            // decode the message using the bucket
            char[] msgArr = message.toCharArray();
            for (int i = 0; i < msgArr.length; i++) {
                if (msgArr[i] == ' ') {
                    result.append(" ");
                } else {
                    result.append(bucket.get(msgArr[i]));
                }
            }
            return result.toString();
        }
    }
}