support hinting literals in CP-SAT Python

ortools/sat/python/cp_model.py

@@ -2939,10 +2939,20 @@ class CpModel:
         """
         return swig_helper.CpSatHelper.write_model_to_file(self.__model, file)
 
-    def add_hint(self, var: IntVar, value: int) -> None:
+    @overload
+    def add_hint(self, var: IntVar, value: int) -> None: ...
+
+    @overload
+    def add_hint(self, literal: BoolVarT, value: bool) -> None: ...
+
+    def add_hint(self, var, value) -> None:
         """Adds 'var == value' as a hint to the solver."""
-        self.__model.solution_hint.vars.append(self.get_or_make_index(var))
-        self.__model.solution_hint.values.append(value)
+        if var.index >= 0:
+            self.__model.solution_hint.vars.append(self.get_or_make_index(var))
+            self.__model.solution_hint.values.append(int(value))
+        else:
+            self.__model.solution_hint.vars.append(self.negated(var.index))
+            self.__model.solution_hint.values.append(int(not value))
 
     def clear_hints(self):
         """Removes any solution hint from the model."""

ortools/sat/python/cp_model_test.py

@@ -1428,6 +1428,21 @@ class CpModelTest(absltest.TestCase):
         self.assertEqual(2, solver.value(x))
         self.assertEqual(4, solver.value(y))
 
+    def testSolutionHintingWithBooleans(self):
+        print("testSolutionHintingWithBooleans")
+        model = cp_model.CpModel()
+        x = model.new_bool_var("x")
+        y = model.new_bool_var("y")
+        model.add_linear_constraint(x + y, 1, 1)
+        model.add_hint(x, True)
+        model.add_hint(~y, True)
+        solver = cp_model.CpSolver()
+        solver.parameters.cp_model_presolve = False
+        status = solver.solve(model)
+        self.assertEqual(cp_model.OPTIMAL, status)
+        self.assertTrue(solver.boolean_value(x))
+        self.assertFalse(solver.boolean_value(y))
+
     def testStats(self):
         print("testStats")
         model = cp_model.CpModel()