add quick sort

Author: umaaamm

C++/quicksort.cpp

@@ -0,0 +1,71 @@
+// C++ Implementation of the Quick Sort Algorithm.
+#include <iostream>
+using namespace std;
+ 
+int partition(int arr[], int start, int end)
+{
+ 
+    int pivot = arr[start];
+ 
+    int count = 0;
+    for (int i = start + 1; i <= end; i++) {
+        if (arr[i] <= pivot)
+            count++;
+    }
+ 
+    // Giving pivot element its correct position
+    int pivotIndex = start + count;
+    swap(arr[pivotIndex], arr[start]);
+ 
+    // Sorting left and right parts of the pivot element
+    int i = start, j = end;
+ 
+    while (i < pivotIndex && j > pivotIndex) {
+ 
+        while (arr[i] <= pivot) {
+            i++;
+        }
+ 
+        while (arr[j] > pivot) {
+            j--;
+        }
+ 
+        if (i < pivotIndex && j > pivotIndex) {
+            swap(arr[i++], arr[j--]);
+        }
+    }
+ 
+    return pivotIndex;
+}
+ 
+void quickSort(int arr[], int start, int end)
+{
+ 
+    // base case
+    if (start >= end)
+        return;
+ 
+    // partitioning the array
+    int p = partition(arr, start, end);
+ 
+    // Sorting the left part
+    quickSort(arr, start, p - 1);
+ 
+    // Sorting the right part
+    quickSort(arr, p + 1, end);
+}
+ 
+int main()
+{
+ 
+    int arr[] = { 9, 3, 4, 2, 1, 8 };
+    int n = 6;
+ 
+    quickSort(arr, 0, n - 1);
+ 
+    for (int i = 0; i < n; i++) {
+        cout << arr[i] << " ";
+    }
+ 
+    return 0;
+}