fix CPPLINT in sorting folder

(cherry picked from commit 7efa52e067)

sorting/counting_sort_string.cpp

@@ -0,0 +1,41 @@
+// C++ Program for counting sort
+#include <iostream>
+
+using namespace std;
+
+void countSort(string arr)
+{
+
+    string output;
+
+    int count[256], i;
+    for (int i = 0; i < 256; i++)
+        count[i] = 0;
+
+    for (i = 0; arr[i]; ++i)
+        ++count[arr[i]];
+
+    for (i = 1; i <= 256; ++i)
+        count[i] += count[i - 1];
+
+    for (i = 0; arr[i]; ++i)
+    {
+        output[count[arr[i]] - 1] = arr[i];
+        --count[arr[i]];
+    }
+
+    for (i = 0; arr[i]; ++i)
+        arr[i] = output[i];
+
+    cout << "Sorted character array is " << arr;
+}
+
+int main()
+{
+    string arr;
+    cin >> arr;
+
+    countSort(arr);
+
+    return 0;
+}