Added counting sort in cpp (#56)

* add binary search in js

* added merge sort in c

* added quick sort in cpp

* modified quick sort

* added heap sort

* updated readme.md

* added counting sort

sorting/README.md

@@ -8,6 +8,8 @@
 4. [Merge Sort](c-or-cpp/merge-sort.c)
 5. [Quick Sort](c-or-cpp/quick-sort.cpp)
 6. [Heap Sort](c-or-cpp/heap-sort.cpp)
+7. [Counting Sort](c-or-cpp/counting-sort.cpp)
+
 
 ### C#
 

sorting/c-or-cpp/counting-sort.cpp

@@ -0,0 +1,57 @@
+#include <iostream>
+#include <algorithm>
+using namespace std;
+
+//function to find the max element from the array
+int getMax(int a[], int size)
+{
+    int max = a[1];
+    for (int i = 2; i <= size; i++)
+    {
+        if (a[i] > max)
+            max = a[i];
+    }
+    return max;
+}
+void countSort(int *a, int size);
+
+int main()
+{
+    cout << "Enter the length of array" << endl;
+    int n;
+    cin >> n;
+    int *a = new int(n + 1);
+    // Getting elements of array
+    cout << "Enter the elements of array" << endl;
+    for (int i = 1; i <= n; i++)
+        cin >> a[i];
+    cout << "Original array: \n";
+    for (int i = 1; i <= n; i++)
+        cout << a[i] << " ";
+    countSort(a, n);
+    cout << "\nSorted array: \n";
+    for (int i = 1; i <= n; i++)
+        cout << a[i] << " ";
+    delete (a);
+    return 0;
+}
+
+void countSort(int *a, int size)
+{
+    int output[size + 1];
+    int max = getMax(a, size);
+    int count[max + 1]; //create count array (max+1 number of elements)
+    for (int i = 0; i <= max; i++)
+        count[i] = 0; //initialize count array to all zero
+    for (int i = 1; i <= size; i++)
+        count[a[i]]++; //increase number count in count array.
+    for (int i = 1; i <= max; i++)
+        count[i] += count[i - 1]; //find cumulative frequency
+    for (int i = size; i >= 1; i--)
+    {
+        output[count[a[i]]] = a[i];
+        count[a[i]] -= 1; //decrease count for same numbers
+    }
+    for (int i = 1; i <= size; i++)
+        a[i] = output[i]; //store output array to main array
+}