adding skiena's algorithm and challenges courses

These courses are important resources for people preparing for programming competitions or interview questions

Author: crmackay

extras/courses.md

@@ -64,7 +64,9 @@ Courses | Duration | Effort
 
 Courses | Duration | Effort
 :-- | :--: | :--:
-[Analysis of Algorithms](https://www.coursera.org/course/aofa)| 6 weeks | 6-8 hours/week
+[Analysis of Algorithms (Skiena)](http://www3.cs.stonybrook.edu/~skiena/373/) | 15 weeks | 6-8 hours/week 
+[Analysis of Algorithms (Sedgewick)](https://www.coursera.org/course/aofa)| 6 weeks | 6-8 hours/week
+[Programming Challenges (Skiena)](http://www3.cs.stonybrook.edu/~skiena/392/) | 14 weeks | 6-8 hours/week
 
 ### Programming Paradigms
 
@@ -175,4 +177,4 @@ Courses | Duration | Effort
 [Internet of Things: Setting Up Your DragonBoard™ Development Platform](https://www.coursera.org/learn/internet-of-things-dragonboard/)| 10 weeks | 2-3 hours/week
 [Internet of Things: Sensing and Actuation From Devices](https://www.coursera.org/learn/internet-of-things-sensing-actuation)| 6 weeks | 3-5 hours/week
 [Internet of Things: Communication Technologies](https://www.coursera.org/learn/internet-of-things-communication)| 4 weeks | 1 hours/week
-[Internet of Things: MultimediaTechnologies](https://www.coursera.org/learn/internet-of-things-multimedia)| 3 weeks | 1-2 hours/week
+[Internet of Things: MultimediaTechnologies](https://www.coursera.org/learn/internet-of-things-multimedia)| 3 weeks | 1-2 hours/week