Here are several literary elements in "A & P" in no particular order:

• We have a theme, in this case often described as a "coming of age" story.  The main character, Sammy, evolves from a rather cynical, bored teenager to a person who takes a stand on principal against an authority figure, his boss at the A & P, who, from Sammy's perspective, mistreats the girls
• Dialogue--Updike's use of dialogue gives us insights into the personalities of Sammy, Stocksie, the "Queen," and Sammy's boss
• The minor theme of irony--Sammy takes his stand, partly in hopes of impressing the prettiest girl, but she is long gone by the time he actually quits and walks out the door.
• Satire--Sammy makes no secret of his disdain for the average customers in the A & P, essentially calling them sheep and herd animals.  And there is implied satire in the scene in which the manager tells the girls that they are not properly dressed for the market--this is a market in a beach town in summer where their attire should not be unexpected.
• Lastly, stock literary elements include plot (Sammy's evolution or coming of age), narrative (what happens in the story), characterization (mostly through dialogue for everyone but Sammy), and a narrator/point of view (first person).