[jkami]

I really don't understand when to use の and when to use が

I always connect nouns and adjectives using が

For example:

髪が長いです。

But when I use 頭がいい人, my teacher says it should be 頭のいい人.

Is it because there is another noun 人 after the adjective いい?


Which of the following is correct?

髪が長い人? 髪の長い人?