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    <p>I borrowed heavily from <a href="https://stackoverflow.com/users/216517/st0le">st0le</a>'s <a href="https://stackoverflow.com/a/3078491/300257">answer</a>.</p> <p>Basically, as I iterated through the bit array that was controlling the set generation, I checked to make sure that the number of bits was between the minimum and maximum.</p> <p>Here's the code.</p> <pre><code>import java.util.BitSet; import java.util.Iterator; import java.util.Set; import java.util.TreeSet; public class PowerSet&lt;E&gt; implements Iterator&lt;Set&lt;E&gt;&gt;, Iterable&lt;Set&lt;E&gt;&gt; { private int minSize; private int maxSize; private E[] arr = null; private BitSet bset = null; @SuppressWarnings("unchecked") public PowerSet(Set&lt;E&gt; set, int minSize, int maxSize) { this.minSize = Math.min(minSize, set.size()); this.maxSize = Math.min(maxSize, set.size()); arr = (E[]) set.toArray(); bset = new BitSet(arr.length + 1); for (int i = 0; i &lt; minSize; i++) { bset.set(i); } } @Override public boolean hasNext() { return !bset.get(arr.length); } @Override public Set&lt;E&gt; next() { Set&lt;E&gt; returnSet = new TreeSet&lt;E&gt;(); // System.out.println(printBitSet()); for (int i = 0; i &lt; arr.length; i++) { if (bset.get(i)) { returnSet.add(arr[i]); } } int count; do { incrementBitSet(); count = countBitSet(); } while ((count &lt; minSize) || (count &gt; maxSize)); // System.out.println(returnSet); return returnSet; } protected void incrementBitSet() { for (int i = 0; i &lt; bset.size(); i++) { if (!bset.get(i)) { bset.set(i); break; } else bset.clear(i); } } protected int countBitSet() { int count = 0; for (int i = 0; i &lt; bset.size(); i++) { if (bset.get(i)) { count++; } } return count; } protected String printBitSet() { StringBuilder builder = new StringBuilder(); for (int i = 0; i &lt; bset.size(); i++) { if (bset.get(i)) { builder.append('1'); } else { builder.append('0'); } } return builder.toString(); } @Override public void remove() { throw new UnsupportedOperationException("Not Supported!"); } @Override public Iterator&lt;Set&lt;E&gt;&gt; iterator() { return this; } public static void main(String[] args) { Set&lt;Character&gt; set = new TreeSet&lt;Character&gt;(); for (int i = 0; i &lt; 7; i++) set.add((char) (i + 'A')); PowerSet&lt;Character&gt; pset = new PowerSet&lt;Character&gt;(set, 3, 5); int count = 1; for (Set&lt;Character&gt; s : pset) { System.out.println(count++ + ": " + s); } } } </code></pre> <p>And here are the test results:</p> <pre><code>1: [A, B, C] 2: [A, B, D] 3: [A, C, D] 4: [B, C, D] 5: [A, B, C, D] 6: [A, B, E] 7: [A, C, E] 8: [B, C, E] 9: [A, B, C, E] 10: [A, D, E] 11: [B, D, E] 12: [A, B, D, E] 13: [C, D, E] 14: [A, C, D, E] 15: [B, C, D, E] 16: [A, B, C, D, E] 17: [A, B, F] 18: [A, C, F] 19: [B, C, F] 20: [A, B, C, F] 21: [A, D, F] 22: [B, D, F] 23: [A, B, D, F] 24: [C, D, F] 25: [A, C, D, F] 26: [B, C, D, F] 27: [A, B, C, D, F] 28: [A, E, F] 29: [B, E, F] 30: [A, B, E, F] 31: [C, E, F] 32: [A, C, E, F] 33: [B, C, E, F] 34: [A, B, C, E, F] 35: [D, E, F] 36: [A, D, E, F] 37: [B, D, E, F] 38: [A, B, D, E, F] 39: [C, D, E, F] 40: [A, C, D, E, F] 41: [B, C, D, E, F] 42: [A, B, G] 43: [A, C, G] 44: [B, C, G] 45: [A, B, C, G] 46: [A, D, G] 47: [B, D, G] 48: [A, B, D, G] 49: [C, D, G] 50: [A, C, D, G] 51: [B, C, D, G] 52: [A, B, C, D, G] 53: [A, E, G] 54: [B, E, G] 55: [A, B, E, G] 56: [C, E, G] 57: [A, C, E, G] 58: [B, C, E, G] 59: [A, B, C, E, G] 60: [D, E, G] 61: [A, D, E, G] 62: [B, D, E, G] 63: [A, B, D, E, G] 64: [C, D, E, G] 65: [A, C, D, E, G] 66: [B, C, D, E, G] 67: [A, F, G] 68: [B, F, G] 69: [A, B, F, G] 70: [C, F, G] 71: [A, C, F, G] 72: [B, C, F, G] 73: [A, B, C, F, G] 74: [D, F, G] 75: [A, D, F, G] 76: [B, D, F, G] 77: [A, B, D, F, G] 78: [C, D, F, G] 79: [A, C, D, F, G] 80: [B, C, D, F, G] 81: [E, F, G] 82: [A, E, F, G] 83: [B, E, F, G] 84: [A, B, E, F, G] 85: [C, E, F, G] 86: [A, C, E, F, G] 87: [B, C, E, F, G] 88: [D, E, F, G] 89: [A, D, E, F, G] 90: [B, D, E, F, G] 91: [C, D, E, F, G] </code></pre>
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    1. POJAVA : generating power set with subset length between 3 and a max
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    1. USGilbert Le Blanc
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    1. COgreat !! c'est genial ;) Thanks a lot. For now it works very well with small number, i'll try it with bigger =)
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      1. USNikkolasg
 

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