Many people use endl and '\n' interchangeably without understanding the key difference between the functioning of the two.

Sometimes using endl in place of '\n' can end up getting you a TLE which otherwise would have been an AC with the use of '\n'.

So let's see what the difference is.

'\n' : It inserts a new line to the output stream.

endl : It inserts a new line and flushes the output stream.

So eventually

cout<<endl;

is equivalent to using

cout<<'\n'<<flush;

Conclusion

Using '\n' outperforms endl in terms of speed (or time) when matter is related to new line only.

Related Problem

The problem which I solved and got TLE issue was Escape from Stones. Go and have a shot at it.