Vettel wins the title if:
He finishes in the top four
He finishes fifth, sixth or seventh and Alonso doesn't win
He finishes eighth or ninth and Alonso is third or lower
He finishes 10th or worse and Alonso is not on the podium
Alonso wins the title if:
He wins and Vettel is fifth or lower
He is second and Vettel eighth or lower
He is third and Vettel is 10th or lower