Was the Fictional Character Sir Lancelot Inspired by King Ladislaus I of Hungary?

In brief: Yes, he was. But if you are also interested in how and why certain mythical episodes of  the eleventh-century Hungarian King's life seeped into the Arthurian legends, read Stephen Pow's latest article about Lancelot and Ladislaus (László) in the latest issue of CEU's Annual of Medieval Studies (2018).