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POGenerating all subsets of characters in a string using recursion, JAVA
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  1. POGenerating all subsets of characters in a string using recursion, JAVA
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    copied!<p>Forgive me if I mess this up, this is my first question. I've been working on this problem for hours. It is supposed to generate all subsets of characters (<strong><em>not necessarily substrings</em></strong>) in a string, using recursion. I commented it a lot so you could see my thinking and hopefully tell me where I'm going wrong. I'm using Eclipse as an IDE if that makes any difference.</p> <pre><code> import java.util.ArrayList; //Generates subsets of a string public class SubsetGenerator { private String original; private String remaining; private ArrayList&lt;String&gt; subsets; //Constructs a subset generator //@param input string to have subsets generated public SubsetGenerator(String input) { original = input; remaining = original; subsets = new ArrayList&lt;String&gt;(); } public void printSubsets() { System.out.print(subsets); } //gets subsets public void generateSubsets() { //if the string is empty, it has no subsets if(remaining.length() == 1) { subsets.add(remaining); return; } else { //remove the first character and hold onto it String removed = remaining.substring(0,1); remaining = remaining.substring(1); //recursion. Eventually it should add the last character in the string to the ArrayList and return generateSubsets(); //Take each element that is in the ArrayList, add the removed character to it, add this back to the list for (int i = 0; i &lt; subsets.size(); i++) { String temp = removed + subsets.get(i); subsets.add(temp); } subsets.add(removed);//add the removed character by itself return; } } } </code></pre> <p>These are the errors I'm getting:</p> <pre><code>Exception in thread "main" java.lang.OutOfMemoryError: Java heap space at java.util.Arrays.copyOfRange(Arrays.java:3221) at java.lang.String.&lt;init&gt;(String.java:233) at java.lang.StringBuilder.toString(StringBuilder.java:447) at SubsetGenerator.generateSubsets(SubsetGenerator.java:41) at SubsetGenerator.generateSubsets(SubsetGenerator.java:37) at SubsetGenerator.generateSubsets(SubsetGenerator.java:37) at SubsetGenerator.generateSubsets(SubsetGenerator.java:37) at SubsetGeneratorTester.main(SubsetGeneratorTester.java:7) </code></pre> <p>I've tested it with this code:</p> <pre><code>public class SubsetGeneratorTester { public static void main(String[] args) { SubsetGenerator s = new SubsetGenerator("world"); s.generateSubsets(); s.printSubsets(); } } </code></pre>
 

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