quicksort.js (HarshCasper#1319)

* Create quicksort.js

* Update quicksort.js

* Update README.md

Co-authored-by: Abhinav Anand <[email protected]>

JavaScript/README.md

@@ -34,6 +34,7 @@
 - [Bubble Sort](./sort/BubbleSort.js)
 - [Insertion Sort](./sort/insertion_sort.js)
 - [Sleep Sort](./sort/sleepSort.js)
+- [Quick Sort](./sort/quicksort.js)
 
 ## Machine Learning
 

JavaScript/sort/quicksort.js

@@ -0,0 +1,56 @@
+/*
+What is Quick Sort?
+
+Quick Sort algorithm follows Divide and Conquer approach.
+It divides elements into smaller parts based on some condition and
+performing the sort operations on those divided smaller parts.
+
+Time Complexity : O(N*logN)
+*/
+
+var items = [5,3,7,6,2,9];
+function swap(items, leftIndex, rightIndex){
+    var temp = items[leftIndex];
+    items[leftIndex] = items[rightIndex];
+    items[rightIndex] = temp;
+}
+function partition(items, left, right) {
+    var pivot = items[Math.floor((right + left) / 2)], //middle element
+        i = left,                                      //left pointer
+        j = right;                                     //right pointer
+    while (i <= j) {
+        while (items[i] < pivot) {
+            i++;
+        }
+        while (items[j] > pivot) {
+            j--;
+        }
+        if (i <= j) {
+            swap(items, i, j);                        //sawpping two elements
+            i++;
+            j--;
+        }
+    }
+    return i;
+}
+
+function quickSort(items, left, right) {
+    var index;
+    if (items.length > 1) {
+        index = partition(items, left, right);       //index returned from partition
+        if (left < index - 1) {                      //more elements on the left side of the pivot
+            quickSort(items, left, index - 1);
+        }
+        if (index < right) {                         //more elements on the right side of the pivot
+            quickSort(items, index, right);
+        }
+    }
+    return items;
+}
+
+// first call to quick sort
+
+var sortedArray = quickSort(items, 0, items.length - 1);
+console.log(sortedArray);
+
+//prints [2,3,5,6,7,9]