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  1. /* package whatever; // don't place package name! */
  2.  
  3. import java.util.ArrayList;
  4. import java.util.List;
  5. import java.util.stream.Collectors;
  6.  
  7. /* Name of the class has to be "Main" only if the class is public. */
  8. class Ideone {
  9.     private static final String[] keys;
  10.     private static final String[] values;
  11.  
  12.     static {
  13.         String alphabet = "abcdefghijklmnopqrstuvwxyz";
  14.         keys = new String[alphabet.length()];
  15.         values = new String[alphabet.length()];
  16.         for (int i = 0; i < alphabet.length(); i++) {
  17.             keys[i] = String.valueOf(i + 1);
  18.             values[i] = alphabet.substring(i, i + 1);
  19.         }
  20.     }
  21.  
  22.  
  23.     public static List<String> decode(String input) {
  24.         List<String> results = new ArrayList<>();
  25.         decodeRecursive(input, "", results);
  26.         return results;
  27.     }
  28.  
  29.     private static void decodeRecursive(String input, String current, List<String>results) {
  30.         if (input.length() == 0) {
  31.             results.add(current);
  32.             return;
  33.         }
  34.  
  35.         for (int i = 0; i < keys.length; i++) {
  36.             String key = keys[i];
  37.             if (input.startsWith(key)) {
  38.                 decodeRecursive(input.substring(key.length()), current + values[i], results);
  39.             }
  40.         }
  41.     }
  42.  
  43.     public static void main(String[] args) {
  44. 		for (String encoded : new String[]{"1123", "123456"}) {
  45. 			String decoded = decode(encoded).stream().collect(Collectors.joining("\n  "));
  46. 			System.out.printf("Input %s decodes as:\n  %s\n", encoded, decoded);
  47. 		}
  48. 	}
  49. }
Success #stdin #stdout 0.19s 3359744KB
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stdin
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Standard input is empty
stdout
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Input 1123 decodes as:
  aabc
  aaw
  alc
  kbc
  kw
Input 123456 decodes as:
  abcdef
  awdef
  lcdef
https://ideone.com/sozgXb
language:
Java (HotSpot 12)
created:
7 years ago
visibility:
public

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