Insertion in the singly linked list at the beginning

We just need to make a few adjustments in the node links to insert a new element into a singly linked list at the beginning. This process involves the below steps:

  • Use the below statements to allocate the space for the new node. It also stores the data into the data part of the node.
    ptr = (struct node *) malloc(sizeof(struct node *));  
    ptr → data = item   
    
  • Use the below statement to make the linked part of the new node pointing to the existing first node of the list.
    ptr->next = head;  
    
  • Use the below statement to make the new node as the first node of the list.
    head = ptr;  
    

Algorithm

  • Step 1: IF pointer = NULL Then Go to step 7 that is exit otherwise follow step2 [END OF IF]
  • Step 2: SET New_Node = pointer
  • Step 3: SET pointer = pointer → next
  • Step 4: SET New_Node → data= value
  • Step 5: SET New_Node →next =head
  • Step 6: SET head = New_Node
  • Step 7: Exit

C Example:

#include  
#include  
void beginInsert(int);  
struct node  
{  
    int data;  
    struct node *next;  
};  
struct node *head;  
void main ()  
{  
    int choice,element;  
    do   
    {  
        printf("\nEnter the element to insert:\n");  
        scanf("%d",&element);  
        beginInsert(element);  
        printf("\nPress 0 to insert more elements.\n");  
        scanf("%d",&choice);  
    }while(choice == 0);  
}  
void beginInsert(int element)  
    {  
        struct node *ptr = (struct node *)malloc(sizeof(struct node *));  
        if(ptr == NULL)  
        {  
            printf("\nOVERFLOW - Exit\n");  
        }  
        else  
        {  
            ptr->data = element;  
            ptr->next = head;  
            head = ptr;  
            printf("\nNode successfully inserted.\n");  
        }  
 
    }

Output

Enter the element to insert:
2

Node successfully inserted.

Press 0 to insert more elements.
0

Enter the element to insert:
4

Node successfully inserted.

Press 0 to insert more elements.
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