add Week 2

Author: SSQ

README.md

@@ -14,8 +14,16 @@ Notebook for quick search can be found [here](https://ssq.github.io/2017/07/17/C
  - [Big-oh notation](https://github.com/SSQ/Coursera-Stanford-Divide-and-Conquer-Sorting-and-Searching-and-Randomized-Algorithms/blob/master/Lecture%20Slides/2.2-slides_algo-asymptotic1_typed.pdf);
  - [Omega and Theta notation](https://github.com/SSQ/Coursera-Stanford-Divide-and-Conquer-Sorting-and-Searching-and-Randomized-Algorithms/blob/master/Lecture%20Slides/2.4-slides_algo-asymptotic3_typed.pdf);
 
-- Week 2:
-
+- Week 2 Lecture slides:
+ - 3: Divide and Conquer:
+ - [Counting Inversions](https://github.com/SSQ/Coursera-Stanford-Divide-and-Conquer-Sorting-and-Searching-and-Randomized-Algorithms/blob/master/Lecture%20Slides/3.2-slides_algo-inversions2_typed.pdf)
+ - [Implementation](https://github.com/SSQ/Coursera-Stanford-Divide-and-Conquer-Sorting-and-Searching-and-Randomized-Algorithms/tree/master/Programming%20Assignment%202)
+ - [Matrix Multiplication](https://github.com/SSQ/Coursera-Stanford-Divide-and-Conquer-Sorting-and-Searching-and-Randomized-Algorithms/blob/master/Lecture%20Slides/3.3-slides_algo-strassen_typed.pdf) Strassen’s Algorithm
+ - [Closest Pair](https://github.com/SSQ/Coursera-Stanford-Divide-and-Conquer-Sorting-and-Searching-and-Randomized-Algorithms/blob/master/Lecture%20Slides/3.4-slides_algo-closest1_typed.pdf) Optional
+ - 4: The Master Method:
+ - [Motivation](https://github.com/SSQ/Coursera-Stanford-Divide-and-Conquer-Sorting-and-Searching-and-Randomized-Algorithms/blob/master/Lecture%20Slides/4.1-slides_algo-master1_typed.pdf)
+ - [Example](https://github.com/SSQ/Coursera-Stanford-Divide-and-Conquer-Sorting-and-Searching-and-Randomized-Algorithms/blob/master/Lecture%20Slides/4.3-slides_algo-master3_typed.pdf)
+ - [Proof I](https://github.com/SSQ/Coursera-Stanford-Divide-and-Conquer-Sorting-and-Searching-and-Randomized-Algorithms/blob/master/Lecture%20Slides/4.4-slides_algo-master4_typed.pdf), [Proof II](https://github.com/SSQ/Coursera-Stanford-Divide-and-Conquer-Sorting-and-Searching-and-Randomized-Algorithms/blob/master/Lecture%20Slides/4.6-slides_algo-master6_typed.pdf)
 - Week 3:
 
 - Week 4: