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*
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*
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package samples.integer;
import org.kohsuke.args4j.Option;
import samples.AbstractProblem;
import solver.Solver;
import solver.constraints.ICF;
import solver.constraints.IntConstraintFactory;
import solver.search.loop.monitors.SMF;
import solver.search.strategy.ISF;
import solver.variables.IntVar;
import solver.variables.VariableFactory;
import util.tools.StringUtils;
/**
* Costas Arrays
* "Given n in N, find an array s = [s_1, ..., s_n], such that
* <ul>
* <li>s is a permutation of Z_n = {0,1,...,n-1};</li>
* <li>the vectors v(i,j) = (j-i)x + (s_j-s_i)y are all different </li>
* </ul>
* <br/>
* An array v satisfying these conditions is called a Costas array of size n;
* the problem of finding such an array is the Costas Array problem of size n."
* <br/>
*
* @author Jean-Guillaume Fages
* @since 25/01/11
*/
public class CostasArrays extends AbstractProblem {
@Option(name = "-o", usage = "Costas array size.", required = false)
private static int n = 14; // should be <15 to be solved quickly
IntVar[] vars, vectors;
@Override
public void createSolver() {
solver = new Solver("CostasArrays");
}
@Override
public void buildModel() {
vars = VariableFactory.enumeratedArray("v", n, 0, n - 1, solver);
vectors = new IntVar[(n*(n-1))/2];
IntVar[][] diff = new IntVar[n][n];
int idx = 0;
for (int i = 0; i < n; i++) {
for (int j = i+1; j < n; j++) {
IntVar k = VariableFactory.enumerated(StringUtils.randomName(), -n, n, solver);
solver.post(ICF.arithm(k,"!=",0));
solver.post(IntConstraintFactory.sum(new IntVar[]{vars[i],k},vars[j]));
vectors[idx] = VariableFactory.offset(k, 2 * n * (j - i));
diff[i][j] = k;
idx++;
}
}
solver.post(IntConstraintFactory.alldifferent(vars, "AC"));
solver.post(IntConstraintFactory.alldifferent(vectors, "BC"));
// symmetry-breaking
solver.post(ICF.arithm(vars[0],"<",vars[n-1]));
}
@Override
public void configureSearch() {
SMF.limitTime(solver,20000);
solver.set(ISF.lexico_LB(vectors));
}
@Override
public void solve() {
solver.findSolution();
}
@Override
public void prettyOut() {
String s = "";
for (int i = 0; i < n; i++) {
s += "|";
for (int j = 0; j < n; j++) {
if (j == vars[i].getValue()) {
s += "x|";
} else {
s += "-|";
}
}
s += "\n";
}
System.out.println(s);
}
public static void main(String[] args) {
new CostasArrays().execute(args);
}
}