chore(C): add circular linked list (#325)

Co-authored-by: Arsenic <54987647+Arsenic-ATG@users.noreply.github.com>

algorithms/C/README.md

@@ -10,6 +10,7 @@
 ## Linked Lists
 - [Insert and Delete at Beginning](linked-lists/Insert-and-delete-beginning.c)
 - [Josephus Problem](linked-lists/josephus-problem.c)
+- [Circular Linked List](linked-lists/Insert-and-del-beginning-circular-ll.c)
 
 ## Queues
 - [Double Ended Queue using array](queues/double-ended-queue-using-array.c)

algorithms/C/linked-lists/Insert-and-del-beginning-circular-ll.c

@@ -0,0 +1,114 @@
+
+//Circular Linked List
+//insertion and Deletion at the beginning of the Linked List
+#include <stdio.h>
+#include <stdlib.h>
+
+//  Structure Definition
+
+// 1. Data of Integer type.
+// 2. Pointer to the Next Node .
+struct node {
+    int data ;
+    struct node *next ;
+} ;
+struct node *head = NULL ;
+// Use tail pointer to avoid traversing the Linked List while inserting of the new created node
+// because after every insertion of a new node we need to point make the last node point to the newly created Node 
+struct node *tail = NULL ;
+
+void printList(){
+
+    if(head == NULL)
+    {
+        printf("\nList is empty");
+        return;
+    }
+
+    else{
+        printf("\nItem in the Linked List are :  ");
+        // Initialize the ptr(pointer) with head location .
+        struct node *ptr = head ;
+        do{
+            printf("%d ",ptr->data) ; // Print the value of the Node
+            ptr = ptr->next ;         // Increment the ptr 
+        }while(ptr != head);          // While Loop until we encounter a Node pointer ptr not pointing to the same location as head .
+
+    }
+}
+
+
+void insertBeg(int data){
+// create a link
+   struct node *new_node = (struct node*) malloc(sizeof(struct node)) ;
+
+   if(new_node==NULL){
+       printf("\nCannot create the Node");
+       return;
+   }
+
+   else{
+       new_node->data=data;
+       if(head==NULL){
+            // making the head and the tail pointer to point to the newly created node
+            head = new_node ;
+            tail = new_node;
+       }
+       else{
+            // Point the new_node pointer to the current head
+            new_node->next = head ;
+            head = new_node ;
+        }
+
+        // making the tail pointer to point to the new head
+        tail->next=head;
+    }
+}
+
+// Deletion at the Beginning of the Circular Linked List
+
+void deleteBeg(){
+    // NO Deletion when list is empty
+    if(head == NULL) {
+        printf("\ndeletion not possible ( List is empty )");
+        return;
+    }
+
+    // There is only one node left in the list
+    else if(head == tail)
+    {
+        free(head);
+        head = NULL;
+        tail = NULL;
+        return;
+    }
+
+    else{
+        // Store head location in a temporary Node pointer.
+        struct node *temp = head ;
+
+        head = head->next ;
+        tail->next=head;
+
+        free(temp);
+    }
+}
+
+int main(){
+
+    insertBeg(10);  // Insert 10 at Beginning
+    insertBeg(20);  // Insert 20 at Beginning
+    insertBeg(30);  // Insert 30 at Beginning
+    insertBeg(40);  // Insert 40 at Beginning
+    insertBeg(50);  // Insert 50 at Beginning
+    insertBeg(60);  // Insert 60 at Beginning
+
+    printList();    // Prints : 60 50 40 30 20 10
+
+    deleteBeg();    // Delete First Element
+
+    printList();    // Prints : 50 40 30 20 10
+
+    return 0 ;
+}
+