linked_list.c

/*Single linked list operations*/

#include <stdio.h>
#include <stdlib.h>

struct node
{
    int data;
    struct node* link;
};

struct node* root = NULL;
int len;

void append();
void addatbegin();
void addatafter();
int length();
void display();
void delete();

void main()
{
    int ch;
    while (1)
    {
        printf("Single linked list operations: \n");
        printf("1. Append\n");
        printf("2. Add at begin\n");
        printf("3. Add at after\n");
        printf("4. Length\n");
        printf("5. Display\n");
        printf("6. Delete\n");
        printf("7. Quit\n");

        printf("Enter your choice: ");
        scanf("%d", &ch);

        switch(ch)
        {
            case 1: append();
                    break;
            case 2: addatbegin();
                    break;
            case 3: addatafter();
                    break;
            case 4: len = length();
                    printf("Length: %d \n\n", len);
                    break;
            case 5: display();
                    break;
            case 6: delete();
                    break;
            case 7: exit(0);
            default: ("Invalid choice\n\n");
        }
    }
}

void append()
{
    struct node* temp;
    temp = (struct node*)malloc(sizeof(struct node));

    printf("Enter node data: ");
    scanf("%d", &temp->data);
    temp->link = NULL;

    if (root == NULL)       //list is empty
    {
        root = temp;
    }
    else
    {
        struct node* p;
        p = root;

        while(p->link != NULL)
        {
            p = p->link;
        }
        p->link = temp;
    }
}

int length()
{
    int count = 0;
    struct node* temp;
    temp = root;
    while(temp != NULL)
    {
        count++;
        temp = temp->link;
    }
    return count;
}

void display()
{
    struct node* temp;
    temp = root;
    if (temp == NULL)
    {
        printf("The list is empty\n\n");
    }
    else
    {
        while(temp != NULL)
        {
            printf("%d-->", temp->data);
            temp = temp->link;
        }
        printf("\n\n");
    }
}

void addatbegin()
{
    struct node* temp;
    temp = (struct node*)malloc(sizeof(struct node));
    printf("Enter node data: ");
    scanf("%d", &temp->data);
    temp->link = NULL;
    if (root == NULL)
    {
        root = temp;
    }
    else 
    {
        temp->link = root;
        root = temp;
    }
}

void addatafter()
{
    struct node* temp, * p;
    int loc, i = 1;
    printf("Enter location: ");
    scanf("%d", &loc);
    len = length();
    if (loc > len)
    {
        printf("Invalid location\n");
        printf("List is having %d nodes\n", len);
    }
    else
    {
        p = root;
        while (i<loc)
        {
            p = p->link;
            i++;
        }
        temp = (struct node*)malloc(sizeof(struct node));
        printf("Enter node data: ");
        scanf("%d", &temp->data);
        temp->link = NULL;
        temp->link = p->link;
        p->link = temp;
    }
}

void delete()
{
    struct node* temp;
    int loc;
    printf("Enter location to delete: ");
    scanf("%d", &loc);
    len = length();
    if (loc > len)
    {
        printf("Invalid location");
    }
    else if (loc == 1)
    {
        temp = root;
        root = temp->link;
        temp->link = NULL;
        free(temp);
    }
    else
    {
        struct node* p = root, * q;
        int i = 1;
        while (i < loc-1)
        {
            p = p->link;
            i++;
        }
        q = p->link;
        p->link = q->link;
        q->link = NULL;
        free(q);
    }
}