Update dnf-sort.cpp

algorithms/CPlusPlus/Sorting/dnf-sort.cpp

@@ -1,3 +1,8 @@
+
+// C++ program to sort an array
+// with 0, 1 and 2 using dnf sort which also stands for  “Dutch National Flag algorithm”
+
+
 #include <bits/stdc++.h>
 using namespace std;
 
@@ -53,3 +58,7 @@ int main()
 
     return 0;
 }
+
+
+// Time Complexity: O(n), Only one traversal of the array is needed.
+// Space Complexity: O(1), No extra space is required.