Add solutions for questions 46 to 50 in 99 Haskell problems.
Add solutions for questions 46 to 50 in 99 Haskell problems.

timtian090/Playground,timtian090/Playground,timtian090/Playground,timtian090/Playground,timtian090/Playground,timtian090/Playground,timtian090/Playground,timtian090/Playground,timtian090/Playground