What is episode when ash's swadloon evolve?

Ash's Swadloon evolves into Leavanny in the episode titled "The Battle of the Samurai," which is the 19th episode of the Pokémon Black & White series. In this episode, Ash and his friends encounter a Pokémon battle involving a Samurai and his Leavanny, which inspires Swadloon to evolve during battle. This evolution signifies Swadloon's growth and strength as a Pokémon.