It seems that in C++11, even with the standard ios::sync_with_stdio(0), cin.tie(0); hacks, has significantly slower I/O with cin/cout than C++14.

View these submissions:
- cin/cout && C++11: 2963ms here
- cin/cout && C++14: 1934ms here

With scanf/printf, this issue isn't there:
- scanf/printf && C++11: 2027ms here
- scanf/printf && C++14: 1887ms here

I was unaware of this. Does anybody have any explanations? Am I missing something specific about my submissions?

Thanks ed1d1a8d for the discussion.