enh(CPlusPlus): circular linked lists (#353)

* Code Refactor

This refactors the previous code to make it more readable and user friendly

* Fixed bug and added useful comments

* Fixed Typo

algorithms/CPlusPlus/Linked-Lists/circular.cpp

@@ -1,39 +1,54 @@
+//Description : Creating Circular linked list
+
 #include <iostream>
 using namespace std;
+
 struct Node {
-   int data;
+    int data;
-   struct Node *next;
+    Node * next;
+    Node(int x) {
+        data = x;
+        next = NULL;
+    }
 };
-struct Node* head = NULL;
+Node * insertion(int newdata, Node * head) {  //Insertion at the end of linked list
-void insert(int newdata) {
+    Node * newnode = new Node(newdata);       //Creating a new node with value newdata
-   struct Node *newnode = (struct Node *)malloc(sizeof(struct Node));
+    Node * ptr = head;
-   struct Node *ptr = head;
+    if (head == NULL) {                       //If the list was initially empty then return the newnode as the new head 
-   newnode->data = newdata;
+        newnode -> next = newnode;
-   newnode->next = head;
+        return newnode;
-   if (head!= NULL) {
+    }
-      while (ptr->next != head)
+    while (ptr -> next != head) {            //Traversing till we reach the last node
-      ptr = ptr->next;
+        ptr = ptr -> next;
-      ptr->next = newnode;
+    }
-   } else
+    newnode -> next = ptr -> next;          //Insert the new node at the end of the list
-   newnode->next = newnode;
+    ptr -> next = newnode;
-   head = newnode;
+    return head;
+
 }
-void display() {
+
-   struct Node* ptr;
+void display(Node * head) {                //Function to print items in the list
-   ptr = head;
+    Node * ptr = head;
-   do {
+    if (head == NULL) {
-      cout<<ptr->data <<" ";
+        cout << "Empty Circular Linked List";
-      ptr = ptr->next;
+        return;
-   } while(ptr != head);
+    }
+    do {
+        cout << ptr -> data << " ";
+        ptr = ptr -> next;
+    }
+    while (ptr != head);
 }
-int main() {
+
-   insert(3);
+int main() {                            //Main Driver function
-   insert(1);
+    Node * head = NULL;
-   insert(7);
+    head = insertion(3, head);
-   insert(3);
+    head = insertion(4, head);
-   insert(1);
+    head = insertion(5, head);
-   insert(7);
+    head = insertion(6, head);
-   cout<<"The circular linked list is: ";
+    head = insertion(1, head);
-   display();
+    head = insertion(7, head);
-   return 0;
+    display(head);
+    return 0;
+
 }