I know the answer but its from a famous Greek story, I think.
Is it Oedipus, where he travels for a while and comes across this village that has this giant harassing it?

That's the Riddle of the Sphinx--four legs (not one leg) in the morning, etc.

The Riddle of the Sphinx

The sphinx? Is that the being that Oedipus goes up against?

From Wikipedia --

Many years later, Oedipus is told by a drunk that Polybus is not his real father but when he asks his parents, they deny it. Oedipus seeks counsel from the same Delphic Oracle. The Oracle does not tell him the identity of his true parents but instead tells him that he is destined to kill his father and marry his mother. In his attempt to avoid the fate predicted by the Oracle, he decides to not return home to Corinth. Since it is near to Delphi, Oedipus decides to go to Thebes.

Oedipus encounters a Sphinx which would stop all those who traveled to Thebes and ask them a riddle. If the travelers were unable to answer correctly, they were killed and eaten by the sphinx; if they were successful, they would be able to continue their journey. The riddle was: "What walks on four feet in the morning, two in the afternoon and three at night?". Oedipus answers: "Man; as an infant, he crawls on all fours, as an adult, he walks on two legs and, in old age, he relies on a walking stick". Oedipus was the first to answer the riddle correctly. Having heard Oedipus' answer, the Sphinx is astounded and inexplicably kills itself by throwing itself into the sea, freeing Thebes.

Grateful, the people of Thebes appoint Oedipus as their king and give him the recently widowed Queen Jocasta's hand in marriage.

Oedipus - Wikipedia, the free encyclopedia