/** * Template method, which can be configured by overriding the three * primitive operations below. */ private Assignment recursiveBackTrackingSearch(CSP csp, Assignment assignment) { Assignment result = null; if (assignment.isComplete(csp.getVariables())) { result = assignment; } else { Variable var = selectUnassignedVariable(assignment, csp); foreach (Object value in orderDomainValues(var, assignment, csp)) { assignment.setAssignment(var, value); fireStateChanged(assignment, csp); if (assignment.isConsistent(csp.getConstraints(var))) { DomainRestoreInfo info = inference(var, assignment, csp); if (!info.isEmpty()) { fireStateChanged(csp); } if (!info.isEmptyDomainFound()) { result = recursiveBackTrackingSearch(csp, assignment); if (result != null) { break; } } info.restoreDomains(csp); } assignment.removeAssignment(var); } } return(result); }