C Program to Remove Duplicates from a Linked List

This C Program to remove duplicate elements from a linked list.

Here is source code of the C Program to remove duplicate elements from a linked list. The C program is successfully compiled and run on a Linux system. The program output is also shown below.

```
/*
```

 * C Program to Remove Duplicates from a Linked List

```
 */
```
```
#include <stdio.h>
```
```
#include <stdlib.h>
```
```
 
```
```
struct node
```
```
{
```
```
    int num;
```
```
    struct node *next;
```
```
};
```
```
 
```
```
void create(struct node **);
```
```
void dup_delete(struct node **);
```
```
void release(struct node **);
```
```
void display(struct node *);
```
```
 
```
```
int main()
```
```
{
```
```
    struct node *p = NULL;
```
```
    struct node_occur *head = NULL;
```
```
    int n;
```
```
 
```

    printf("Enter data into the list\n");

```
    create(&p);
```

    printf("Displaying the nodes in the list:\n");

```
    display(p);
```

    printf("Deleting duplicate elements in the list...\n");

```
    dup_delete(&p);
```

    printf("Displaying non-deleted nodes in the list:\n");

```
    display(p);
```
```
    release(&p);
```
```
 
```
```
    return 0;
```
```
}
```
```
 
```
```
void dup_delete(struct node **head)
```
```
{
```
```
    struct node *p, *q, *prev, *temp;
```
```
 
```
```
    p = q = prev = *head;
```
```
    q = q->next;
```
```
    while (p != NULL)
```
```
    {
```

        while (q != NULL && q->num != p->num)

```
        {
```
```
            prev = q;
```
```
            q = q->next;
```
```
        }
```
```
        if (q == NULL)
```
```
        {
```
```
            p = p->next;
```
```
            if (p != NULL)
```
```
            {
```
```
                q = p->next;
```
```
            }
```
```
        }
```
```
        else if (q->num == p->num)
```
```
        {
```
```
            prev->next = q->next;
```
```
            temp = q;
```
```
            q = q->next;
```
```
            free(temp);
```
```
        }
```
```
    }
```
```
}
```
```
 
```
```
void create(struct node **head)
```
```
{
```
```
    int c, ch;
```
```
    struct node *temp, *rear;
```
```
 
```
```
    do
```
```
    {
```
```
        printf("Enter number: ");
```
```
        scanf("%d", &c);
```

        temp = (struct node *)malloc(sizeof(struct node));

```
        temp->num = c;
```
```
        temp->next = NULL;
```
```
        if (*head == NULL)
```
```
        {
```
```
            *head = temp;
```
```
        }
```
```
        else
```
```
        {
```
```
            rear->next = temp;
```
```
        }
```
```
        rear = temp;
```

        printf("Do you wish to continue [1/0]: ");

```
        scanf("%d", &ch);
```
```
    } while (ch != 0);
```
```
    printf("\n");
```
```
}
```
```
 
```
```
void display(struct node *p)
```
```
{
```
```
    while (p != NULL)
```
```
    {
```
```
        printf("%d\t", p->num);
```
```
        p = p->next;
```
```
    }
```
```
    printf("\n");
```
```
}
```
```
 
```
```
void release(struct node **head)
```
```
{
```
```
    struct node *temp = *head;
```
```
    *head = (*head)->next;
```
```
    while ((*head) != NULL)
```
```
    {
```
```
        free(temp);
```
```
        temp = *head;
```
```
        (*head) = (*head)->next;
```
```
    }
```
```
}
```

$ cc duplicate.c 
$ ./a.out
Enter data into the list
Enter number: 1
Do you wish to continue [1/0]: 1
Enter number: 2
Do you wish to continue [1/0]: 1
Enter number: 1
Do you wish to continue [1/0]: 1
Enter number: 3
Do you wish to continue [1/0]: 1
Enter number: 2
Do you wish to continue [1/0]: 1
Enter number: 4
Do you wish to continue [1/0]: 0
 
Displaying the nodes in the list:
1	2	1	3	2	4	
Deleting duplicate elements in the list...
Displaying non-deleted nodes in the list:
1	2	3	4

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