Merge branch 'master' into major-corrections-to-files

data_structure/doubly_linked_list.cpp

@@ -61,6 +61,7 @@ void double_linked_list::remove(int x) {
     t->prev->next = t->next;
     t->next->prev = t->prev;
   }
+  delete t;
 }
 
 void double_linked_list::search(int x) {

sorting/quick_sort.cpp

@@ -1,15 +1,49 @@
-/* C implementation QuickSort */
+/**
+ *
+ *      copyright The Algorithms
+ *      Author - 
+ *      Correction - ayaankhan98
+ *
+ * Implementation Details -
+ *      Quick Sort is a divide and conquer algorithm. It picks and element as
+ *      pivot and partition the given array around the picked pivot. There
+ *      are many different versions of quickSort that pick pivot in different
+ *      ways.
+ *
+ *      1. Always pick the first element as pivot
+ *      2. Always pick the last element as pivot (implemented below)
+ *      3. Pick a random element as pivot
+ *      4. Pick median as pivot
+ *
+ *      The key process in quickSort is partition(). Target of partition is,
+ *      given an array and an element x(say) of array as pivot, put x at it's
+ *      correct position in sorted array and put all smaller elements (samller
+ *      than x) before x, and put all greater elements (greater than x) after
+ *      x. All this should be done in linear time
+ *
+ */
+
+#include <cstdlib>
 #include <iostream>
 
+/**
+ *      This function takes last element as pivot, places  
+ *      the pivot element at its correct position in sorted  
+ *      array, and places all smaller (smaller than pivot)  
+ *      to left of pivot and all greater elements to right  
+ *      of pivot 
+ *
+ */
+
 int partition(int arr[], int low, int high) {
-    int pivot = arr[high];  // pivot
-    int i = (low - 1);      // Index of smaller element
+    int pivot = arr[high];    // taking the last element as pivot
+    int i = (low - 1);        // Index of smaller element
 
     for (int j = low; j < high; j++) {
         // If current element is smaller than or
         // equal to pivot
         if (arr[j] <= pivot) {
-            i++;  // increment index of smaller element
+            i++;   // increment index of smaller element
             int temp = arr[i];
             arr[i] = arr[j];
             arr[j] = temp;
@@ -21,17 +55,26 @@ int partition(int arr[], int low, int high) {
     return (i + 1);
 }
 
+
+/** 
+ *      The main function that implements QuickSort  
+ *      arr[] --> Array to be sorted,  
+ *      low --> Starting index,  
+ *      high --> Ending index 
+*/
 void quickSort(int arr[], int low, int high) {
     if (low < high) {
         int p = partition(arr, low, high);
-
         quickSort(arr, low, p - 1);
         quickSort(arr, p + 1, high);
     }
 }
 
+// prints the array after sorting
 void show(int arr[], int size) {
-    for (int i = 0; i < size; i++) std::cout << arr[i] << "\n";
+    for (int i = 0; i < size; i++)
+        std::cout << arr[i] << " ";
+    std::cout << "\n";
 }
 
 // Driver program to test above functions