Question

Deletion of node at beginning in singly linked list

Answer 1

Deletion of node at beginning

Algorithm to Delete node from the beginning

Step 1: IF HEAD = NULL Write UNDERFLOW      Go to Step 5     [END OF IF] Step 2: SET PTR = HEAD Step 3: SET HEAD = HEAD -> NEXT Step 4: FREE PTR Step 5: EXIT

Example

Program 

#include <stdio.h>  #include <stdlib.h> struct node {    int data; // Data  struct node *next; // Address } *head;  void createList(int n); void deleteFirstNode();  void displayList(); int main()  { int n, choice; printf("Enter the total number of nodes: ");    scanf("%d", &n);    createList(n);    printf("\nData in the list \n");    displayList(); printf("\nPress 1 to delete first node: ");    scanf("%d", &choice); /* Delete first node from list */    if(choice == 1)    deleteFirstNode();    printf("\nData in the list \n");    displayList();    return 0; }  /* * Create a list of n nodes */ void createList(int n) { struct node *newNode, *temp; int data, i; head = (struct node *)malloc(sizeof(struct node)); /* * If unable to allocate memory for head node */ if(head == NULL) { printf("Unable to allocate memory."); }    else { /* * In data of node from the user */    printf("Enter the data of node 1: "); scanf("%d", &data);   head->data = data; // Link the data field with data head->next = NULL;  // Link the address field to NULL   temp = head; /* * Create n nodes and adds to linked list */    for(i=2; i<=n; i++)    {   newNode = (struct node *)malloc(sizeof(struct node)); /* If memory is not allocated for newNode */ if(newNode == NULL) { printf("Unable to allocate memory.");    break; }    else {    printf("Enter the data of node %d: ", i);    scanf("%d", &data); newNode->data = data; // Link the data field of newNode with data   newNode->next = NULL; // Link the address field of newNode with NULL temp->next = newNode; // Link previous node i.e. temp to the newNode   temp = temp->next; } }    printf("SINGLY LINKED LIST CREATED SUCCESSFULLY\n"); } }    /* * Deletes the first node of the linked list */  void deleteFirstNode() {    struct node *toDelete; if(head == NULL) { printf("List is already empty."); }    else { toDelete = head; head = head->next; printf("\nData deleted = %d\n", toDelete->data);    /* Clears the memory occupied by first node*/    free(toDelete);    printf("SUCCESSFULLY DELETED FIRST NODE FROM LIST\n");    } } /* * Displays the entire list */  void displayList() {    struct node *temp; /* * If the list is empty i.e. head = NULL */ if(head == NULL) {    printf("List is empty."); } else {   temp = head;    while(temp != NULL) { printf("Data = %d\n", temp->data); // Print data of current node   temp = temp->next; // Move to next node } }  }

Output

---

For more Manipal University Jaipur B.Tech CSE-III Sem Data Structure Lab Experiments Click here

---