I found codefights.com to have the most relevant exercises. I have used it for interview prep and just to get a new language under my fingers. Other sites just

I found codefights.com to have the most relevant exercises. I have used it for interview prep and just to get a new language under my fingers. Other sites just haven't cut it for me. Some are heavy on arbitrary math puzzles with little focus on actual coding skills. HackerRank you spend half of every algorithm reading the inputs from stdin. Some you run out of puzzles and just have to repeat.