New Feature - feat: added [quickSort] algorithm

algorithms/sorting/quickSort.js

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+/**
+ * Quick Sort
+ *
+ * Geeks For Geeks
+ * https://www.geeksforgeeks.org/quick-sort/
+ *
+ * Tutorials Point
+ * https://www.tutorialspoint.com/how-to-implement-quick-sort-in-javascript
+ */
+
+/**
+ * Quick Sort:
+ * Quick sort is the sorting technique that follows the divide and conquer approach.
+ * Quick sort is similar to the merge sort algorithm as it uses the divide and conquer
+ * approach to sort the elements.It divides the given list into two halves, calls itself for the two halves and then merges the two sorted halves. We have to define the quicksort() function to perform the merging.
+ * The sub-lists are divided again and again into halves until the list cannot be
+ * divided further. Then we combine all returns of partition algorithm, so on until we get the sorted list.
+ */
+
+/**
+ * Algorithm:
+ * Step 1.Split the given list into two halves.
+ * Step 2.Everytime we call quickSort(a, l, r) we search the new m, which is in the end at the correct position.
+ * Step 3.Repeat step 2 unit with end up with a single sorted array.
+ */
+
+// a is the array, l is left index, r is right index
+function quickSort(a, l, r){
+    if (a[0]<a[a.size-1]){
+        // m is the return of partition
+        //m is now at the correct position
+        m = partition(arr, l, r);
+        quickSort(arr, l, m-1);
+        quickSort(arr, m+1, r);
+    }
+}
+
+function partition(a, l, r){
+    // pivot is the last number of a
+    // m is in the beginning the first number
+    var pivot = a[r];
+    var m = a[l];
+    // this loop exchanges the a[i] position with the a[m] position if i < pivot
+    for (i=0; i<r; i++){
+        if (a[i] < pivot){
+            var help = a[i];
+            a[i] = a[m];
+            a[m] = help;
+            m = m+1;
+        }
+    }
+    // after the loop the position of m is exchanged with the last postion
+    var help = a[m];
+    a[m] = a[r];
+    a[r] = help;
+    // now m is at the correct position and returns
+    return m;
+}
+var arr = [12, 11, 13, 5, 6, 7];
+var arr_size = arr.length;
+
+console.log("Given array is :", arr); // Output: Given array is : [ 12, 11, 13, 5, 6, 7 ]
+
+quickSort(arr, 0, arr.length-1);
+
+console.log("Sorted array is :", arr); // Output: Sorted array is : [ 5, 6, 7, 11, 12, 13 ]