I just saw this question and quite frankly I want to close it, because it can be answered by simply visiting the movie's Wikipedia page. But there isn't a close reason for "lack of research", unfortunately.
Sure, I can downvote it. But chances are some others will upvote it (people even upvote blatantly off-topic questions), and thus this low-quality question will live on. (Right now it already has two upvotes and one person has "starred" the question.)
Back in 2011 it seems there was a process to close such questions, and if I google "hitchcock suspicion original ending" the first link is the Wikipedia entry and the excerpt hints at the answer:
Suspicion (1941) is a romantic psychological thriller directed by Alfred Hitchcock, and starring .... Hitchcock's recollection of this original ending—in his book-length interview with François Truffaut, published in English as Hitchcock/Truffaut in ...
And this isn't the only question like that, I've seen plenty recently.