/**
* Recursive backtracking solution
*
* @param formula 3sat formula to solve.
* @returns true iff formula is satisfiable
*/
public boolean dp(Formula formula) {
if (formula.isEmpty()) // First base case: solution found
return true;
else if (formula.hasEmptyClause()) { // Second base case: dead end found
return false;
} else {
// Pick a branch variable
int var = formula.selectBranchVar();
formula.setVar(var, true);
if (dp(formula)) return true;
else {
// Unset var in the formula
formula.unset(var);
// Setting var to true did not work, so now try var = false
formula.setVar(var, false);
if (dp(formula)) return true;
else {
// Neither true nor false worked, so unset the branch
// variable and backtrack
formula.unset(var);
return false;
}
}
}
}
@Test
public void testIsEmpty() {
Formula f = new Formula();
assertTrue(f.isEmpty());
}