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    <p>A simple recursive algorithm can be implemented if you realize that the segmentation of a string <code>s</code> is equal to a set containing <code>s</code> itself, and a set union of each substring <code>X</code> of <code>s</code> with the segmentation of <code>s\X</code>. Also, since you will always have <code>n-1</code> possible substrings, and you can either segment or not segment in each of these points, you will always end up with <code>2^(n-1)</code> segments. </p> <p>It is more simple to understand with an example for the segmentation of the string <code>ABC</code>:</p> <blockquote> <ol> <li>{'ABC'} // 'ABC' itself</li> <li>{'A', 'B, 'C'} // substring 'A' union 1st segmentation of 'BC' = {'B, 'C'}</li> <li>{'A', 'BC'} // substring 'A' union 2nd segmentation of 'BC' = {'BC'}</li> <li>{'AB', 'C'} // substring 'AB' union 1st and only segmentation of 'C' = {'C'}</li> <li>Union of 1, 2, 3, and 4, yield all segmentations of the string <code>ABC</code>.</li> </ol> </blockquote> <p>This translates almost directly to the following implementation:</p> <pre><code>public static Set&lt;Set&lt;String&gt;&gt; segment(String s) { // `s` itself. Set&lt;Set&lt;String&gt;&gt; result = new LinkedHashSet&lt;Set&lt;String&gt;&gt;(); Set&lt;String&gt; root = new LinkedHashSet&lt;String&gt;(); root.add(s); result.add(root); // set union of each substring `X` (prefix) of `s` with `s\X` (rest). for (int i = 1; i &lt; s.length(); i++) { String prefix = s.substring(0, i); String rest = s.substring(i); for (Set&lt;String&gt; segments : segment(rest)) { Set&lt;String&gt; segment = new LinkedHashSet&lt;String&gt;(); segment.add(prefix); segment.addAll(segments); result.add(segment); } } return result; } </code></pre> <p>Sample outputs:</p> <pre><code>System.out.println(segment("ABC")); // [[ABC], [AB, C], [A, B, C], [BC, A]] System.out.println(segment("ABCD")); // [[D, AB, C], [BCD, A], [D, ABC], [D, A, B, C], [AB, CD], [ABCD], [D, BC, A], [A, B, CD]] </code></pre>
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    1. PORecursively spell out a word
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    1. USJoão Silva
    1. USJoão Silva
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    1. COuse LinkedHashSet, please :)
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      1. USbestsss
    2. COWas looking for a recursive algorithm
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      1. USBrendan
    3. CO@Brendan: This is recursive. `segment` is invoked recursively in the `for` loop: `for (Set<String> segments : segment(rest))`.
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      1. USJoão Silva
 

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