Update dnf-sort.cpp

algorithms/CPlusPlus/Sorting/dnf-sort.cpp

@@ -1,6 +1,11 @@
+
+// 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;
- 
+
 // Function to sort the input array,
 // the array is assumed
 // to have values in {0, 1, 2}
@@ -9,22 +14,22 @@ void sort012(int a[], int arr_size)
     int lo = 0;
     int hi = arr_size - 1;
     int mid = 0;
- 
+
     // Iterate till all the elements
     // are sorted
     while (mid <= hi) {
         switch (a[mid]) {
- 
+
         // If the element is 0
         case 0:
             swap(a[lo++], a[mid++]);
             break;
- 
+
         // If the element is 1 .
         case 1:
             mid++;
             break;
- 
+
         // If the element is 2
         case 2:
             swap(a[mid], a[hi--]);
@@ -32,7 +37,7 @@ void sort012(int a[], int arr_size)
         }
     }
 }
- 
+
 // Function to print array arr[]
 void printArray(int arr[], int arr_size)
 {
@@ -40,16 +45,20 @@ void printArray(int arr[], int arr_size)
     for (int i = 0; i < arr_size; i++)
         cout << arr[i] << " ";
 }
- 
+
 // Driver Code
 int main()
 {
     int arr[] = { 0, 1, 1, 0, 1, 2, 1, 2, 0, 0, 0, 1 };
     int n = sizeof(arr) / sizeof(arr[0]);
- 
+
     sort012(arr, n);
- 
+
     printArray(arr, n);
- 
+
     return 0;
 }
+
+
+// Time Complexity: O(n), Only one traversal of the array is needed.
+// Space Complexity: O(1), No extra space is required.