[LeonardA-L]

Last year was Advent of Code ( http://adventofcode.com/ ) and while they did not name them, each exercise was based on a known algorithmic problem (knapsack, traveling salesman, ...), and it was a fun way to engage people in a "1 exercise a day" pattern.

I guess you can also try your hand at CodinGame's puzzles ( https://www.codingame.com/training ) as they also involve known algorithms and they are realy fun to play.

But ultimately, both of these resources won't teach you how to implement algorithms.