I find that I always spend a lot of time on thinking problems.
For many times I can't pass the problem although I have thought out the solution because that thinking took me too much time so that I have no time to code.
What should I do to change this situation?
Thanks a lot!

Although I have been training for nearly three years and have participated almost 20 contests on this ID, but I still cannot become a Specialist.
In fact, I have learned many advanced algorithms, even including Link Cut Tree and polynomial multi-point evaluation, but I even find it difficult to pass the D problem of Div.2, which requires almost no any difficult algorithms.
I find that I always fail to observe the properties of the problem or get stuck in corner cases for a long time.
I have seen many friends who have been training with me successfully become Specialists or even Experts, and I feel a bit anxious.
Do you have any good ideas about this? I will be extremely grateful!