From f84976ab8369b350b76801d680ae371166c855c0 Mon Sep 17 00:00:00 2001
From: Satyam Singh <56315878+satcasm@users.noreply.github.com>
Date: Sun, 31 Jan 2021 18:20:51 +0530
Subject: [PATCH] added quick sort (#48)

* add binary search in js

* added merge sort in c

* added quick sort in cpp

* modified quick sort
---
 sorting/README.md                   |  1 +
 sorting/c-or-cpp/merge-sort.c       | 13 +++--
 sorting/c-or-cpp/quick-sort.cpp     | 77 +++++++++++++++++++++++++++++
 sorting/c-or-cpp/selection-sort.cpp |  2 +-
 4 files changed, 85 insertions(+), 8 deletions(-)
 create mode 100644 sorting/c-or-cpp/quick-sort.cpp

diff --git a/sorting/README.md b/sorting/README.md
index 84457784..b00bbae7 100644
--- a/sorting/README.md
+++ b/sorting/README.md
@@ -6,6 +6,7 @@
 2. [Insertion Sort](c-or-cpp/insertion-sort.cpp)
 3. [Selection Sort](c-or-cpp/selection-sort.cpp)
 4. [Merge Sort](c-or-cpp/merge-sort.c)
+5. [Quick Sort](c-or-cpp/quick-sort.cpp)
 
 ### C#
 
diff --git a/sorting/c-or-cpp/merge-sort.c b/sorting/c-or-cpp/merge-sort.c
index cdc64ae8..3d66da6e 100644
--- a/sorting/c-or-cpp/merge-sort.c
+++ b/sorting/c-or-cpp/merge-sort.c
@@ -13,11 +13,11 @@ int main()
     printf("Enter the elements of the array:\n");
     for (int i = 0; i < n; i++)
         scanf("%d", &a[i]);
-    printf( "Given array is: ");
+    printf("Given array is: ");
     for (int i = 0; i < n; i++)
         printf("%d ", a[i]);
     mergeSort(a, 0, n - 1);
-    printf( "\nSorted array is: ");
+    printf("\nSorted array is: ");
     for (int i = 0; i < n; i++)
         printf("%d ", a[i]);
     return 0;
@@ -30,7 +30,7 @@ void merging(int a[], int l, int m, int r)
 {
     int n1 = m - l + 1;
     int n2 = r - m;
-    int Left[n1], Right[n2];        // Creating temporary arrays
+    int Left[n1], Right[n2]; // Creating temporary arrays
 
     // Copy data to temp arrays Left[] and Right[]
     for (int i = 0; i < n1; i++)
@@ -55,7 +55,7 @@ void merging(int a[], int l, int m, int r)
     }
 
     // Copy the remaining elements of
-	// Left[], if there are any
+    // Left[], if there are any
     while (p < n1)
     {
         a[k] = Left[p];
@@ -64,7 +64,7 @@ void merging(int a[], int l, int m, int r)
     }
 
     // Copy the remaining elements of
-	// Right[], if there are any
+    // Right[], if there are any
     while (q < n2)
     {
         a[k] = Right[q];
@@ -73,10 +73,9 @@ void merging(int a[], int l, int m, int r)
     }
 }
 
-
 // l is for left index and r is
 // right index of the sub-array
-// of arr to be sorted 
+// of arr to be sorted
 void mergeSort(int a[], int l, int r)
 {
     if (l < r)
diff --git a/sorting/c-or-cpp/quick-sort.cpp b/sorting/c-or-cpp/quick-sort.cpp
new file mode 100644
index 00000000..d20a357a
--- /dev/null
+++ b/sorting/c-or-cpp/quick-sort.cpp
@@ -0,0 +1,77 @@
+#include <iostream>
+using namespace std;
+int partition(int a[],int low,int high);
+void quickSort(int a[], int low, int high);
+
+// Driver Code
+int main()
+{
+    cout<<"Enter the length of array"<<endl;
+	int n;
+	cin>>n;
+	int *a = new int(n);
+	// Getting elements of array
+	cout<<"Enter the elements of array"<<endl;
+	for (int i = 0; i < n; i++)
+		cin>>a[i];
+    cout << "Original array: \n";
+    for (int i = 0; i < n; i++)
+        cout << a[i] << " ";
+    quickSort(a, 0, n - 1);
+    cout << "\nSorted array: \n";
+    for (int i = 0; i < n; i++)
+        cout << a[i] << " ";
+    delete (a);
+    return 0;
+}
+
+// A utility function to swap two elements
+void swap(int *a, int *b)
+{
+    int t = *a;
+    *a = *b;
+    *b = t;
+}
+
+/* This function takes last element as pivot, places 
+the pivot element at its correct position in sorted 
+aay, and places all smaller (smaller than pivot) 
+to left of pivot and all greater elements to right 
+of pivot */
+int partition(int a[], int low, int high)
+{
+    int pivot = a[high]; 
+    int i = (low - 1);   
+
+    for (int j = low; j <= high - 1; j++)
+    {
+        // If current element is smaller than the pivot
+        if (a[j] < pivot)
+        {
+            i++; // increment index of smaller element
+            swap(&a[i], &a[j]);
+        }
+    }
+    swap(&a[i + 1], &a[high]);
+    return (i + 1);
+}
+
+/* The main function that implements QuickSort 
+a[] --> array to be sorted, 
+low --> Starting index, 
+high --> Ending index */
+void quickSort(int a[], int low, int high)
+{
+    if (low < high)
+    {
+        /* pi is partitioning index, a[p] is now 
+		at right place */
+        int pi = partition(a, low, high);
+
+        // Separately sort elements before
+        // partition and after partition
+        quickSort(a, low, pi - 1);
+        quickSort(a, pi + 1, high);
+    }
+}
+
diff --git a/sorting/c-or-cpp/selection-sort.cpp b/sorting/c-or-cpp/selection-sort.cpp
index 629f0eb2..e8c3f698 100644
--- a/sorting/c-or-cpp/selection-sort.cpp
+++ b/sorting/c-or-cpp/selection-sort.cpp
@@ -1,4 +1,4 @@
-# include <iostream>
+#include <iostream>
 using namespace std;
 
 int main(int argc, char const *argv[])