Simple Java code written during a Live Coding session (~30min.) solving the "Compte est bon" game, which aims at finding all the operations to apply to a list of numbers to get an expected result. Warning: this source code is not optimized, and could be better, but the goal was to write it quickly in some kind of competition ;)

LCEB.java

import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;

public class LCEB {
  public List<String> resolve(final List<Integer> numbers,
			final Integer expected) {
		return getSolutions(expected, numbers, null, null);

	}

	protected List<String> getSolutions(final Integer expected,
			final List<Integer> numbers, final Integer result,
			final String operation) {
		final List<String> results = new ArrayList<String>();
		if (expected.equals(result))
			results.add(operation);
		else {
			final Iterator<Integer> iterator = numbers.iterator();
			while (iterator.hasNext()) {
				final Integer selected = iterator.next();
				final List<Integer> rest = new ArrayList<Integer>(numbers);
				rest.remove(selected);
				if (result == null)
					results.addAll(getSolutions(expected, rest, selected,
							selected.toString()));
				else {
					results.addAll(getSolutions(expected, rest, result
							+ selected,
							"(" + operation + " + " + selected.toString() + ")"));
					results.addAll(getSolutions(expected, rest, result
							- selected,
							"(" + operation + " - " + selected.toString() + ")"));
					results.addAll(getSolutions(expected, rest, result
							* selected,
							"(" + operation + " * " + selected.toString() + ")"));
					if (result % selected == 0)
						results.addAll(getSolutions(expected, rest, result
								/ selected,
								"(" + operation + " / " + selected.toString()
										+ ")"));
				}
			}
		}
		return results;
	}

}