Okay, but the solution is still bugged, you can check by yourself on DartPad with a1 = [2, 2, 3]; a2 = [4, 9];

it didn't have to pass that test because it isn't actually one of the tests

How this solution passed the test: a1 = [2, 2, 3]; a2 = [4, 9];? solution returns true, however actually it should be false
because this solution doesn't check multiplicity