Freshman Klay Thompson had 15 points and, Aron Baynes had 12 points and nine rebounds for the Cougars (11-8, 3-4).
With 49 seconds to go, Marcus Johnson made a jump shot to give USC the lead for good at 42-41. Hackett sank two free throws with 15 seconds left for a 3-point lead for the Trojans. He then added a free throw with 12 seconds remaining and another free throw with five seconds left to put USC up 46-41.
Thompson then missed a layup that would have cut the Trojans' lead to 46-43.
Taylor Rocheste, the Cougars' leading scorer, didn't score in the opening half and contributed only six points. He made a 3-pointer as time expired.
Washington State led 19-18 at halftime and was ahead most of the second half, holding a 38-33 with 5:28 to play.
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