import choco.kernel.solver.search.integer.AbstractIntVarSelector;
import choco.kernel.solver.variables.integer.IntDomainVar;
import choco.kernel.solver.variables.AbstractVar;
import choco.kernel.memory.IStateInt;

public class StaticMinDegreeHeuristic extends AbstractIntVarSelector {

    private IntDomainVar[] vars;                // 0/1 decision variables
    private int n;                              // number of decision variables
    private IStateInt[] deg;                    // degree of v[i] in candidate set, reversible
    private ReversibleSortedArray candidateSet; // the uninstantiated variables

    private void sort(){ // into ascending order
	int[] degree = new int[n];
	int tempD = -1;
	IntDomainVar tempV = null;
	for (int i=0;i<n;i++) degree[i] = deg[i].get();
	for (int i=n-1;i>0;i--)
	    for (int j=0;j<i;j++)
		if (degree[j] > degree[j+1]){
		    tempD = degree[j];
		    degree[j] = degree[j+1];
		    degree[j+1] = tempD;
		    tempV = vars[j];
		    vars[j] = vars[j+1];
		    vars[j+1] = tempV;
		}
    }

    public StaticMinDegreeHeuristic(IntDomainVar[] vars,IStateInt[] deg,ReversibleSortedArray candidateSet){
	this.vars = vars; n = vars.length;this.deg = deg; this.candidateSet = candidateSet;
	sort();
    }

    public IntDomainVar selectIntVar(){
	for (int i=0;i<n;i++) if (!vars[i].isInstantiated()) return vars[i];
	return null;
    }
}