insert_and_delete_beginning.c (#59)

* ADD - insert_at_beginning

This is a program to add item at the beginning of linked list . Structure Based Implementation .

* Changed FIle Named  .

File name was changed in accordance with the contribution guidelines .

* Changed c++ file to c . 

The file is updated and named was also changed

* Fixed Bug .

change the type of main function from void to int .
Fixed the edge cases for the deletion .

linked-lists/c-or-cpp/Insert_and_delete_beginning.c

@@ -0,0 +1,71 @@
+#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 ;
+struct node *current = NULL ;
+
+//Function to Print the Linked List
+void printList(){
+    printf("\nItem in the Linked List are :  ");
+    // Intialize the ptr(pointer) with head location .
+    struct node *ptr = head ;
+    // While Loop until we encounter a Node which is NULL .
+    // NULL ,  signifies we are the end of the list .
+    while(ptr!=NULL){
+        printf("%d ",ptr->data) ;  //Print the value of the Node
+        ptr = ptr->next ;         //Increment the ptr
+    }
+}
+
+//Insertion at the Beginning of the Linked List
+
+void insertBeg(int data){
+ //Creating a link
+ //Malloc is for space allocation .
+ struct node *link = (struct node*) malloc(sizeof(struct node)) ;
+ link->data = data ;
+ //Point the link's pointer to the current head
+ link->next = head ;
+ //Update the Head to the node we want to insert at the beggining
+ head = link ;
+}
+
+//Deletion at the Beginning of the Linked List
+
+struct node* deleteBeg(){
+  //Case of Underflow (Deletion when list is empty)
+   if(head == NULL) {
+    printf("List is Empty , deletion not possible") ;
+    return NULL ;
+   }
+  //Store head location in a temporary Node .
+  struct node *temp = head ;
+
+  //Update the current Header
+  head = head->next ;
+
+  // returning the deleted Link
+  return temp ;
+
+}
+int main(){
+    deleteBeg();    //Case of Underflow 
+    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 40 20 10
+    deleteBeg();    //Delete First Element
+    printList();    // Prints : 50 40 30 20 10
+    return 0 ;
+}