Doctor Stephen Strange disappeared with the snap in Infinity War. Here is an original theory as to why he isn't dead.

So we were all probably wondering what the heck he was doing when he handed the Time Stone to Thanos. As he was disintegrating, he told Tony "it was the only way" suggesting that it needed to happen for them to win.

Which brings me to my next point.

In the first Doctor Strange movie, when the Ancient One dies, she brings Stephen to a window and shows him the moment she can't see past.

Earlier in Infinity War, Doctor Strange looked into the future to see possibilities and then promptly disintegrates. So if he actually died he
wouldn't be able to see past his death, but he just did. Boom. The end. That's all I got for that one.

Oh yeah, and he has another movie coming up. That too.