Unexpected stuff!

Let’s have a look at this code: int main() { for(int i{0};i<500;i++) { std::cout<<“This is a big number: “<<i*20000000<<std::endl; } } And let’s compile it with g++ using the flag -O3, what’s going to happen? Before answering, let’s have a look at the assembly, shall we? L16: movsbl 39(%ebx), %eax L6: movl %esi, %ecx movl… Continue reading Unexpected stuff!

Subsequences and Fenwick tree’s

Let’s say that we have a sequence A of 1<=n<=10^5 elements, and that this sequence may or may not be ordered but all the numbers {1…n} are present exactly once. And now given 1<=k<=10, you’re asked to find all the increasing sub-sequences of A with exactly k+1 elements. This is a problem I get from a competitive programming… Continue reading Subsequences and Fenwick tree’s

The real keyboard.

Back in the days, when computer were used by real computer users and nobody knew what a mouse is, the preferred input device was also the only input device: The Keyboard! When the hipster revolution began back in the seventies/eighties, the proliferation  of the mouse users increased dramatically, the keyboard was still the preferred computer input… Continue reading The real keyboard.

IO Stream performance.

Many of  the competitive programming portals available on the web advice –for certain problems involving huge input reading or output printing– the user to avoid cin/cout in spite of printf/scanf: As input/output can reach huge size it is recommended to use fast input/output methods: for example, prefer to use scanf/printf instead of cin/cout in C++, prefer to use… Continue reading IO Stream performance.

Labyrinths (not really)

The labyrinthitis is a serious problem* which effect many people, is particularly common in people between the age of 18 to 99 owning a driving license and a car, you may encounter on the road on a daily basis people with this illness! Drive safe out there! If you are confused, well I understand!I’m trying to… Continue reading Labyrinths (not really)

The benefits of SSH

Nowadays people have access to the internet almost from everywhere at every time, and Internet is going to be even more accessible in the near future thanks to brilliant ideas like flying drone with WiFi AC functionlities which are going to allow people from more and more remote areas of the planet to access facebook or… Continue reading The benefits of SSH