Wozniacki began her campaign in the Red Group by dropping just two games against Elina Svitolina and was in similarly destructive form against Halep.
The Romanian failed to win a game in a first set that lasted only 24 minutes and, although she improved in the second set, she could not find the answers she needed and lost 6-0 6-2.
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Wozniacki is now all but guaranteed a place in the semi-finals, while Halep will very likely have to beat Svitolina to reach the last four and keep alive her hopes of finishing the year at the top of the rankings.
Wozniacki told BT Sport: "I felt like I played very well. Obviously she got frustrated and I felt like I was doing everything just a little bit better.
"I feel like I'm back where I'm supposed to be. It's been a great year for me and I'm finishing it off in style."
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