delete function in a singly linked list in c code example

Example 1: delete function in a singly linked list in c

// A complete working C program
// to demonstrate deletion in
// singly linked list
#include <stdio.h>
#include <stdlib.h>
 
// A linked list node
struct Node {
    int data;
    struct Node* next;
};
 
/* Given a reference (pointer to pointer) to the head of a
   list and an int, inserts a new node on the front of the
   list. */
void push(struct Node** head_ref, int new_data)
{
    struct Node* new_node
        = (struct Node*)malloc(sizeof(struct Node));
    new_node->data = new_data;
    new_node->next = (*head_ref);
    (*head_ref) = new_node;
}
 
/* Given a reference (pointer to pointer) to the head of a
   list and a key, deletes the first occurrence of key in
   linked list */
void deleteNode(struct Node** head_ref, int key)
{
    // Store head node
    struct Node *temp = *head_ref, *prev;
 
    // If head node itself holds the key to be deleted
    if (temp != NULL && temp->data == key) {
        *head_ref = temp->next; // Changed head
        free(temp); // free old head
        return;
    }
 
    // Search for the key to be deleted, keep track of the
    // previous node as we need to change 'prev->next'
    while (temp != NULL && temp->data != key) {
        prev = temp;
        temp = temp->next;
    }
 
    // If key was not present in linked list
    if (temp == NULL)
        return;
 
    // Unlink the node from linked list
    prev->next = temp->next;
 
    free(temp); // Free memory
}
 
// This function prints contents of linked list starting
// from the given node
void printList(struct Node* node)
{
    while (node != NULL) {
        printf(" %d ", node->data);
        node = node->next;
    }
}
 
// Driver code
int main()
{
    /* Start with the empty list */
    struct Node* head = NULL;
 
    push(&head, 7);
    push(&head, 1);
    push(&head, 3);
    push(&head, 2);
 
    puts("Created Linked List: ");
    printList(head);
    deleteNode(&head, 1);
    puts("\nLinked List after Deletion of 1: ");
    printList(head);
    return 0;
}

Example 2: how to remove a node from a linked list in c

typedef struct node{
    int value; //this is the value the node stores
    struct node *next; //this is the node the current node points to. this is how the nodes link
}node;

node *rmvNode(node *head, int index){
    node *tmp = head;
    node *rmv;
    int count = 0;

    //base case for if the user enters a value greater then or equal to the length of the head
    //base case for if the user enters a value with a list of length 1. because in this library a list MUST contain one value minimum
    if(index >= len(head) || len(head) == 1){
        return NULL;
    }
  
    //if you want to remove the first value
    if(index == 0){
        rmv = head; //stores the head at this given moment in time
        head = tmp->next; //this jumps the position of the head making sure that the beginning is no longer part of the head
        free(rmv); //this frees the memory given to the initial head
        return head;
    }

    //if you want to remove index position 1
    if(index == 1){
        rmv = head->next;
        head->next = tmp->next->next;
        free(rmv);
        return head;
    }

    //if you want to remove the last value
    if(index == -1){
        
        while(count < len(head)-2){ //we do -2 because we want to access the node before the last one
            tmp = tmp->next;
            count += 1;
        }
        rmv = tmp->next;
        tmp->next = NULL;
        free(rmv);
        return head;
    }

    //remove anything else
    while(count < index-1){
        tmp = tmp->next;
        count += 1;
    }
    rmv = tmp->next;
    tmp->next = tmp->next->next;
    free(rmv);
    return head;

}

Example 3: program to create insert, delete and display operations on singly linked list in c

#include<conio.h>
#include<stdio.h>

struct node
{
    int i;
    struct node *next;
};

void main()
{

    struct node *first;
    struct node *last;

    struct node *temp;
    int ch,user,add,cnt=0,t=0;
    struct node *p;

    clrscr();

    printf("\n\t 1.CREATION");
    printf("\n\t 2.INSERT AT STARTING");
    printf("\n\t 3.INSERT AT MIDDLE(USER'S CHOICE)");
    printf("\n\t 4.INSERT AT END");
    printf("\n\t 5.DELETE 1ST NODE");
    printf("\n\t 6.DELETE LAST NODE");
    printf("\n\t 7.DELETE MIDDLE NODE(USER'S CHOICE)");
    printf("\n\t 8.DISPLAY");
    printf("\n\t 10.EXIT");
    scanf("%d",&user);

    while(user!=10)
    {
      if(user==1)
      {
        printf("\n\t ENTER DATA  ::: ");
        first=(struct node*)malloc(sizeof(struct node));
        scanf("%d",&ch);

        first->i=ch;
        first->next=0;
        p=first;
        cnt=1;
      }
      if(user==2)
      {
            p=(struct node*)malloc(sizeof(struct node));
            printf("\n\t ENTER DATA FOR 1ST NODE");
            scanf("%d",&p->i);
            p->next=first;
            first=p;
            cnt++;
      }
      if(user==4)
      {
            p=(struct node*)malloc(sizeof(struct node));
            printf("\n\t ENTER DATA FOR LAST NODE");
            scanf("%d",&p->i);
            temp=first;
            while(temp->next!=0)
            {
                temp=temp->next;
            }
            temp->next=p;
            p->next=0;
            cnt++;
      }
      if(user==3)
      {
            printf("\n\t ENTER ANY ADDRESS BETWEEN 1 and %d",cnt);
            scanf("%d",&add);

            t=1;
            p=first;
            while(t!=add)
            {
                p=p->next;
                t++;
            }
            temp=(struct node*)malloc(sizeof(struct node));
            printf("\n\t ENTER DATA FOR NODE");
            scanf("%d",&temp->i);
            temp->next=p->next;
            p->next=temp;
            cnt++;
      }
      if(user==5)
      {
            p=first;
            first=p->next;
            free(p);
      }
      if(user==6)
      {
        p=first;
        while(p->next->next!=0)
        {
            p=p->next;
        }
        p->next=0;
        free(p->next->next);
      }
      if(user==8)
      {
        p=first;
        while(p!=0)
        {
            printf("\n\t %d",p->i);
            p=p->next;
        }
      }
      if(user==7)
      {
            printf("\n\t ENTER ANY ADDRESS BETWEEN 1 and %d",cnt);
            scanf("%d",&add);

            t=1;
            p=first;
            while(t<add-1)
            {
                p=p->next;
                t++;
            }
            temp=p->next;
            p->next=temp->next;
            free(temp);
            cnt--;

      }
      printf("\n\t 1.CREATION");
      printf("\n\t 2.INSERT AT STARTING");
      printf("\n\t 3.INSERT AT MIDDLE(USER'S CHOICE)");
      printf("\n\t 4.INSERT AT END");
      printf("\n\t 5.DELETE 1ST NODE");
      printf("\n\t 6.DELETE LAST NODE");
      printf("\n\t 7.DELETE MIDDLE NODE(USER'S CHOICE)");
      printf("\n\t 8.DISPLAY");
      printf("\n\t 10.EXIT");
      scanf("%d",&user);
       }
       getch();
}