Recursion - Java Concepts - page 811

ch13/permute/PermutationGenerator.java

1 import java.util.ArrayList;
2
3 /**
4 This class generates permutations of a
word.
5 */
6 public class PermutationGenerator
7 {
8 /**
9 Constructs a permutation generator.
10 @param aWord the word to permute
11 */
12 public PermutationGenerator(String aWord)
13 {
14 word = aWord;
15 }
16
17 /**
18 Gets all permutations of a given word.
19 */
20 public ArrayList<String> getPermutations()
21 {
22 ArrayList<String> result = new
ArrayList<String>();
23
24 // The empty string has a single permutation: itself
25 if (word.length() == 0 )
26 {
27 result.add(word);
28 return result;
29 }
30
31// Loop through all character positions
32 for ( int i = 0 ; i < word.length(); i++)
33 {
34// Form a simpler word by removing the ith character
35 String shorterWord =
word.substring( 0 , i)
36 + word.substring(i + 1 );

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