Learning and implementing pure algorithms

@admin It'd be very helpful if direct problems on generally used algorithms were included in the practice section, I mean implementing the pure algortihm, no story to go along with it. It's fun to learn a new algorithm by implementing it, it's even more fun to see the implementation get accepted by Online judges :D It'll be helpful for us beginners later to modify them accordingly and solve the problems in challenges. Here's a good list.