Zion Williamson had 31 points to lead all scorers as Duke ousted third-ranked North Carolina in the ACC tournament semifinals on Friday night in Charlotte. (Jeremy Brevard-USA TODAY Sports)

CHARLOTTE — When Duke’s 74-73 gasp over North Carolina on Friday night in an ACC tournament semifinal wedges its way into the memory banks of its 20,116 witnesses and starts primping for the retelling, maybe a 42-second sequence of the second half will rate above all.

Maybe those 42 seconds will outpace the frantic closing seconds, when North Carolina’s Cameron Johnson missed a three-point shot with 18 seconds left that he felt sure felt true, and then Duke’s RJ Barrett missed two free throws with two clangs with 12 seconds left, and then North Carolina’s thrilling Coby White missed a hard fadeaway near the final horn to close the action. Maybe those 32 seconds will override by somewhat the fact that 18-year-old Zion Williamson, the Duke Superman who has enthralled the country, scored with 31 seconds left on an emphatic drive, a miss and an even more emphatic rebound and putback.

Long after Duke finishes playing Florida State on Saturday night in the title game, those 42 seconds could live on, because they told of the outrageous urgency of a game technically meaningless (both teams head for the NCAA tournament next week) yet truthfully heaving and screaming with meaning (it was Duke-North Carolina), just as they told of the spectacle of watching Williamson, the South Carolinian come to play in North Carolina’s favorite long-running spectacle. Maybe they defined this thing long before North Carolina Coach Roy Williams said, “It’s hard right now because our kids really fought like crazy, but they won and that’s the bottom line today.”

The 42 seconds began at the 10:35 mark, when Williamson made a reverse left-handed dunk to give Duke a 59-56 lead long after it trailed 33-20 and Williamson started bailing it out of that. It was not Williamson’s most rule-the-world dunk of the night or of his one and probably only college season. It did not form the most memorable of his 31 points. But it did reveal a bit of his otherworldly dexterity for a 285-pound person, and it did wind up with the big fellow spilled tellingly on the floor.

North Carolina inbounded the ball, and within five seconds it produced something staggering, an utmost turn of the speed it prefers. Garrison Brooks threw it in. White dribbled it once, just once. White delivered it up the court on the left to Brandon Robinson. Robinson caught it and redirected it immediately to Johnson.

Johnson jammed it, and the break had happened so fast it felt hard to process, and the number of dribbles in the entire break had been one, and the arena felt like basketball paradise.

It had more to go.

About 33 seconds more, and North Carolina tried a routine pass out on the perimeter. It did not allow for the fact that a 6-foot-8, 285-pound human with the quickness and hands of — of someone much smaller — would pluck away that pass, roar downcourt and throw in a monstrous dunk with 9:53 left. Duke led 63-58 (with a Cam Reddish score tucked somewhere in that fray), and the place felt both exhausted and exhilarated.

When a reporter asked Barrett to rate the Williamson dunk, Duke Coach Mike Krzyzewski interrupted with coaching language: “It’s two points.”

Barrett then answered, “The one he had today where he took off outside the key on the fastbreak, I give that one a 10.”

Williamson then thanked Barrett with a little fist-bump.

Krzyzewski then said, “Let’s not talk about rating dunks. Let’s talk about the game.”

The game, Krzyzewski said in his 39th Duke season, had been “vintage ‘Duke-Carolina.’” Of course, Williamson had enhanced its vintage. He missed the two regular-season Duke-Carolina games because he sprained his knee near the outset of the first. North Carolina outscored Duke in the paint 94-58 in those games. On Friday, Duke outscored North Carolina in the paint 50-38.

“The guy that’s been hurt came back and put on his Superman jersey again and was incredible,” Williams said. “It’s such a blend of strength and power and quickness that we couldn’t stop him getting the basketball inside and going to the basket.” His 31 points went well with 11 rebounds and a field-goal rate of 13-for-19, giving him 26-for-32 in two games of this tournament.

“He definitely adds a different dimension to their team,” North Carolina’s Johnson said. “He’s a really good athlete and he does a lot of things that they don’t have without him, so it kind of changes the way they play offensively, definitely. And it changes the way they attack.” Beyond that, Johnson saw the same Duke sets, the same North Carolina shots. Maybe a film review could alter that perception, for it would show not only North Carolina’s 4-for-27 from three-point range, and its serial settling for jumpshots, but a moment with 1:29 left, when Luke Maye had a fine turnaround shot available to the left side of the paint, but seemed to change its arc just a smidgen, as would anyone with the thought of Williamson about to fly through the airspace.

It went off the glass and missed.

North Carolina had its 33-20 lead. Duke had Williamson ringing in a three-point shot right after that, then scoring again, then scoring two free throws. Duke had its bench, which Krzyzewski extolled, particularly Jordan Goldwire, whose defense has won his coach’s steep approval, and whose scoop-up of a North Carolina fumble with 1:46 left gave Duke a 72-71 lead after it trailed 71-67. North Carolina had its chance with Johnson’s shot with 18 seconds left, and he said, “I could have bet a thousand dollars right there that that shot was falling but it just didn’t.”

The game had just about everything. It even had a superstar.

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