Bubble sort code added

Author: me-shaon

Sorting/Bubble Sort/README.md

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+# Bubble Sort
+
+**Bubble Sort** is an algorithm which is used to sort **N** elements that are given in a memory for eg: an Array with N number of elements. Bubble Sort compares all the element one by one and sort them based on their values.
+
+It is called Bubble sort, because *with each iteration the smaller element in the list bubbles up towards the first place*, just like a water bubble rises up to the water surface.
+
+Sorting takes place by stepping through all the data items one-by-one in pairs and comparing adjacent data items and swapping each pair that is out of order.
+![bubble sort demonstration](bubble-sort.png)
+
+
+---
+**A visualization on the algorithm:**
+
+Starting from the beginning of the list, compare every adjacent pair, swap their position if they are not in the right order (the latter one is smaller than the former one). After each iteration, one less element (the last one) is needed to be compared until there are no more elements left to be compared.
+
+![Bubble sort gif](https://upload.wikimedia.org/wikipedia/commons/c/c8/Bubble-sort-example-300px.gif)
+
+#### Complexity Analysis
+- Worst Case - O(n<sup>2</sup>)
+- Average Case - O(n<sup>2</sup>)
+- Best Case - O(n)
+
+### More on this topic
+- http://en.wikipedia.org/wiki/Bubble_sort
+- http://quiz.geeksforgeeks.org/bubble-sort/
+- https://www.topcoder.com/community/data-science/data-science-tutorials/sorting/

Sorting/Bubble Sort/bubble-sort.js

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+//Simple Bubble Sort implementation
+function bubbleSort(arr){
+    var len = arr.length;
+
+    for(var i=0; i<len-1; i++){
+        // Last i elements are already in place, so the inner loops will run until it reaches the last i elements
+        for(var j=0; j<len-i-1;j++){
+            //To Sort in decreasing order, change the comparison operator to '<'
+            if(arr[j] > arr[j+1]){
+                var tmp = arr[j];
+                arr[j] = arr[j+1];
+                arr[j+1] = tmp;
+            }
+        }
+    }
+
+    return arr;
+}
+
+//Following is a slightly modified bubble sort implementation, which tracks the list with a flag to check if it is already sorted
+function modifiedBubbleSort(arr){
+    var len = arr.length;
+
+    for(var i=0; i<len-1; i++){
+        var flag = false; //Taking a flag variable
+
+        // Last i elements are already in place, so the inner loops will run until it reaches the last i elements
+        for(var j=0; j<len-i-1;j++){
+            //To Sort in decreasing order, change the comparison operator to '<'
+            if(arr[j] > arr[j+1]){
+                var tmp = arr[j];
+                arr[j] = arr[j+1];
+                arr[j+1] = tmp;
+
+                flag = true; //Setting the flag, if swapping occurs
+            }
+        }
+
+        //If not swapped, that means the list has already sorted
+        if(!flag) break;
+    }
+
+    return arr;
+}
+
+
+/** Testing Bubble 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++){
+    arr.push(getRandomInt(1, 100));
+}
+console.log("Unsorted array: ");
+console.log(arr); //printing unsorted array
+
+arr = bubbleSort(arr);
+// arr = modifiedBubbleSort(arr);
+console.log("Sorted array: ");
+console.log(arr); //printing sorted array