Singly linked list - insert, remove, add, count source code

This snippet submitted by Girish Amara on 2010-08-25. It has been viewed 752282 times.
Rating of 7.3 with 2546 votes
#include<stdio.h>
#include<stdlib.h>

struct node
{
    int data;
    struct node *next;
}*head;



void append(int num)
{
    struct node *temp,*right;
    temp= (struct node *)malloc(sizeof(struct node));
    temp->data=num;
    right=(struct node *)head;
    while(right->next != NULL)
	right=right->next;
    right->next =temp;
    right=temp;
    right->next=NULL;
}



void add( int num )
{
    struct node *temp;
    temp=(struct node *)malloc(sizeof(struct node));
    temp->data=num;
    if (head== NULL)
    {
	head=temp;
	head->next=NULL;
    }
    else
    {
	temp->next=head;
	head=temp;
    }
}
void addafter(int num, int loc)
{
    int i;
    struct node *temp,*left,*right;
    right=head;
    for(i=1;i<loc;i++)
    {
	left=right;
	right=right->next;
    }
    temp=(struct node *)malloc(sizeof(struct node));
    temp->data=num;
    left->next=temp;
    left=temp;
    left->next=right;
    return;
}



void insert(int num)
{
    int c=0;
    struct node *temp;
    temp=head;
    if(temp==NULL)
    {
	add(num);
    }
    else
    {
	while(temp!=NULL)
	{
	    if(temp->data<num)
		c++;
	    temp=temp->next;
	}
	if(c==0)
	    add(num);
	else if(c<count())
	    addafter(num,++c);
	else
	    append(num);
    }
}



int delete(int num)
{
    struct node *temp, *prev;
    temp=head;
    while(temp!=NULL)
    {
	if(temp->data==num)
	{
	    if(temp==head)
	    {
		head=temp->next;
		free(temp);
		return 1;
	    }
	    else
	    {
		prev->next=temp->next;
		free(temp);
		return 1;
	    }
	}
	else
	{
	    prev=temp;
	    temp= temp->next;
	}
    }
    return 0;
}


void  display(struct node *r)
{
    r=head;
    if(r==NULL)
    {
	return;
    }
    while(r!=NULL)
    {
	printf("%d ",r->data);
	r=r->next;
    }
    printf("\n");
}


int count()
{
    struct node *n;
    int c=0;
    n=head;
    while(n!=NULL)
    {
	n=n->next;
	c++;
    }
    return c;
}


int  main()
{
    int i,num;
    struct node *n;
    head=NULL;
    while(1)
    {
	printf("\nList Operations\n");
	printf("===============\n");
	printf("1.Insert\n");
	printf("2.Display\n");
	printf("3.Size\n");
	printf("4.Delete\n");
	printf("5.Exit\n");
	printf("Enter your choice : ");
	if(scanf("%d",&i)<=0){
	    printf("Enter only an Integer\n");
	    exit(0);
	} else {
	    switch(i)
	    {
		case 1:      printf("Enter the number to insert : ");
			     scanf("%d",&num);
			     insert(num);
			     break;
		case 2:     if(head==NULL)
			    {
				printf("List is Empty\n");
			    }
			    else
			    {
				printf("Element(s) in the list are : ");
			    }
			    display(n);
			    break;
		case 3:     printf("Size of the list is %d\n",count());
			    break;
		case 4:     if(head==NULL)
				printf("List is Empty\n");
			    else{
				printf("Enter the number to delete : ");
				scanf("%d",&num);
				if(delete(num))
				    printf("%d deleted successfully\n",num);
				else
				    printf("%d not found in the list\n",num);
			    }
			    break;
		case 5:     return 0;
		default:    printf("Invalid option\n");
	    }
	}
    }
    return 0;
}
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