When a negative question is asked, what is the grammatically correct way to answer? [duplicate]

Possible Duplicate:
How to answer a negative question without ambiguity?
Response to “Would you not do it?”

When a negative question is asked, what is the grammatically correct way to answer? If someone asks you Didn't you come by car today?, what is the correct answer?

Solution 1:

The first question can be answered unambiguously by I came by car today, or I did not come by car today.

(Sorry if that's not quite the answer you were looking for, but in my experience with people, trying both, neither monosyllabic answer works very well across many trials.)

Solution 2:

Due to the inherently ambiguous nature of the question, I prefer to answer this type of inquiry with either "No, I didn't" or "Yes, I did."