<bits/stdc++.h>

[MattC98]

Does #include <bits/stdc++.h> slow your program ?

[Cubbi]

In comparison to including the correct headers, using this internal GCC header may result in slower compilation (not execution):

#include <cstdlib>
int main()
{
    return EXIT_FAILURE;
}

this compiled in 0.1 seconds (best of 5)

$ time g++ -O3 -Wall -pedantic-errors -o test test.cc
real    0m0.136s
user    0m0.046s
sys     0m0.037s

#include <bits/stdc++.h>
int main()
{
    return EXIT_FAILURE;
}

this compiled in 1.5 seconds (best of 5 runs)

$ time g++ -O3 -Wall -pedantic-errors -o test test.cc
real    0m1.533s
user    0m1.303s
sys     0m0.181s

that's 11 times slower

More importantly, "#include <bits/stdc++.h>" means you're no longer using C++: your program can't be used with any other compiler, a future version of GCC may choose to drop or change that header, and you won't be able to use this at work.

[MattC98]

i dont understand the difference between compilation time and execution time, execution time is the one that matters in contests or the compilation time? i dont understand this

[jonnin]

compile time is how long it takes to turn c++ code into an executable program.
execution time is how long it takes your code to run when you USE it.

[Peter87]

"#include <bits/stdc++.h>" means you're no longer using C++

Including a non-standard header file doesn't mean you are not using C++.

[E0p9LyTq]

More importantly, "#include <bits/stdc++.h>" means you're no longer using C++

Just means the C++ being used is non-standard and not portable.

Can be a real headache when the compiler gets upgraded, or use switches to be strict standard conformant.