The ball — and No. 17 Duke’s final chance to tie — bounced off Jayson Tatum’s foot and right to North Carolina State star freshman Dennis Smith Jr.

Smith grabbed it and sprinted to the other end as the final seconds vanished for a stunning 84-82 win in the Blue Devils’ famously hostile Cameron Indoor Stadium. But he didn’t stop when the horn sounded — continuing his downcourt charge, taking off a few steps inside the foul line and throwing down a rim-jarring dunk.

It didn’t matter that the dunk didn’t count. Smith had provided the perfect capper to a spectacular performance Monday night, one that had his teammates mobbing him in celebration the moment he touched down.

“I’m not surprised at all,” Smith said. “A lot of people say it’s an upset. But I planned on winning. I believe our team planned on winning.”

Still, that was something N.C. State (14-7, 3-5 Atlantic Coast Conference) hadn’t done in Cameron since 1995. And this was the same team that had lost four of five coming in, including a 51- point loss at rival North Carolina earlier this month.

Yet N.C. State rallied from 12 down late in the first half, used a 20-5 run to erase a 68- 59 deficit in the final 6? minutes, then got the final stop when Tatum lost control of the ball before getting off a shot to end it for Duke (15-5, 3-4).

It all started with Smith, the point guard and projected lottery pick as a potential one-and-done NBA prospect. Smith finished 10 for 18 from the floor and finished with six assists.

“Dennis is scary,” Duke freshman Frank Jackson said. “We knew that he was capable of and he did it.”

Added Duke associate head coach Jeff Capel: “He’s a very talented kid, and played lights-out basketball tonight.”

Smith was asked about whether he had dreamed of punctuating a big win like that final dunk — which came with teammate Terry Henderson following him downcourt with arms raised in celebration.

“I don’t even know if the dunk counted,” Smith said with a laugh, adding: “I just dreamed of winning big games, regardless of where it’s at.”