Counting sort Code, 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/)

Sorting/Counting Sort/counting_sort.js

@@ -0,0 +1,49 @@
+/* Couting Sort implementation in JavaScript */
+function countingSort(arr) {
+	var i,
+		min = 0,
+		index = 0,
+		aux = [],
+		sortedArray = [];
+
+	var maxVal = Math.max.apply(null, arr); //If the max value of the array given, this line can be removed
+
+	for (i = min; i <= maxVal; i++) { //initializing the auxiliary array with 0
+		aux[i] = 0;
+	}
+
+	for (i = 0; i < arr.length; i++) { //Counting the frequency of the elements
+		aux[arr[i]]++;
+	}
+
+	for (i = min; i <= maxVal; i++) { //based on the frequency, building the new sorted array
+		while (aux[i]-- > 0) {
+			sortedArray[index++] = i;
+		}
+	}
+
+	return sortedArray;
+}
+
+/******************* Testing Selection sort algorithm *********************/
+
+/**
+ * Returns a random integer between min (inclusive) and max (inclusive)
+ * Using Math.round() will give you a non-uniform distribution!
+ */
+function getRandomInt(min, max) {
+	return Math.floor(Math.random() * (max - min + 1)) + min;
+}
+
+var arr = [];
+
+for (var i = 0; i < 10; i++) { //initialize a random integer unsorted array
+	arr.push(getRandomInt(1, 100));
+}
+
+console.log("Unsorted array: ");
+console.log(arr); //printing unsorted array
+
+arr = countingSort(arr);
+console.log("Sorted array: ");
+console.log(arr); //printing sorted array