Counting sort README file added

Author: me-shaon

Sorting/Counting Sort/README.md

@@ -0,0 +1,29 @@
+# Counting Sort
+
+In **Counting sort**, the frequencies of distinct elements of the array to be sorted is counted and stored in an auxiliary array, by mapping its value as an index of the auxiliary array.
+
+![Counting Sort](./images/counting-sort.jpg)
+
+#### Idea:
+
+Let's assume that, array **A** of size **N** needs to be sorted.
+
+- Initialize the auxiliary array **Aux[]** with **0**.
+Note: The size of this array should be greater than the Max value of the elements in **A[]**.
+- Traverse array **A** and store the count of occurrence of each element in the appropriate index of the **Aux** array, which means, execute **Aux[A[i]]++** for each **i**, where **i** ranges from **[0,N−1]**.
+- Initialize the empty array **sortedA[]**
+- Traverse array **Aux** and copy **i** into **sortedA** for **Aux[i]** number of times where **0≤i≤max(A[])**.
+
+Simply speaking, you just need to count the frequency of each of the elements in the given array **A** and based on that frequency count write those elements in a new array, so that we would finally have an array with the sorted elements.
+
+#### Video Tutorial
+<a href="http://www.youtube.com/watch?feature=player_embedded&v=TTnvXY82dtM" target="_blank"><img src="http://img.youtube.com/vi/TTnvXY82dtM/0.jpg"
+alt="Counting Sort (youtube)" width="640" height="480" border="10" /></a>
+
+
+#### Complexity Analysis
+Time Complexity: O(n+k), where **n** is the size of the input array and **k** is the Max value of the elements in the given Array.
+
+### More on this topic
+- [Counting Sort - WikiPedia](https://en.wikipedia.org/wiki/Counting_sort)
+- [Counting Sort - HackerEarth Tutorial](https://www.hackerearth.com/practice/algorithms/sorting/counting-sort/tutorial/)