C Program to Count the Occurrences of Elements in a Linked List

This C Program find the number of occurrences of all elements in a linked list.

Here is source code of the C Program to find the number of occurrences of all elements in 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 Find Number of Occurences of All Elements in a Linked List

```
 */
```
```
#include <stdio.h>
```
```
#include <stdlib.h>
```
```
 
```
```
struct node
```
```
{
```
```
    int num;
```
```
    struct node *next;
```
```
};
```
```
 
```
```
struct node_occur
```
```
{
```
```
    int num;
```
```
    int times;
```
```
    struct node_occur *next;
```
```
};
```
```
 
```
```
void create(struct node **);
```

void occur(struct node *, struct node_occur **);

```
void release(struct node **);
```
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void release_2(struct node_occur **);
```
```
void display(struct node *);
```
```
void disp_occur(struct node_occur *);
```
```
 
```
```
int main()
```
```
{
```
```
    struct node *p = NULL;
```
```
    struct node_occur *head = NULL;
```
```
    int n;
```
```
 
```

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

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    create(&p);
```

    printf("Displaying the occurence of each node in the list:\n");

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    display(p);
```
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    occur(p, &head);
```
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    disp_occur(head);
```
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    release(&p);
```
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    release_2(&head);
```
```
 
```
```
    return 0;
```
```
}
```
```
 
```

void occur(struct node *head, struct node_occur **result)

```
{
```
```
    struct node *p;
```
```
    struct node_occur *temp, *prev;
```
```
 
```
```
    p = head;
```
```
    while (p != NULL)
```
```
    {
```
```
        temp = *result;
```

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

```
        {
```
```
            prev = temp;
```
```
            temp = temp->next;
```
```
        }
```
```
        if (temp == NULL)
```
```
        {
```

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

```
            temp->num = p->num;
```
```
            temp->times = 1;
```
```
            temp->next = NULL;
```
```
            if (*result != NULL)
```
```
            {
```
```
                prev->next = temp;
```
```
            }
```
```
            else
```
```
            {
```
```
                *result = temp;
```
```
            }
```
```
        }
```
```
        else
```
```
        {
```
```
            temp->times += 1;
```
```
        }
```
```
        p = p->next;
```
```
    }
```
```
}
```
```
 
```
```
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 disp_occur(struct node_occur *p)
```
```
{
```

    printf("***************************\n  Number\tOccurence\n***************************\n");

```
    while (p != NULL)
```
```
    {
```

        printf("    %d\t\t%d\n", p->num, p->times);

```
        p = p->next;
```
```
    }
```
```
}
```
```
 
```
```
void release(struct node **head)
```
```
{
```
```
    struct node *temp = *head;
```
```
    *head = (*head)->next;
```
```
    while ((*head) != NULL)
```
```
    {
```
```
        free(temp);
```
```
        temp = *head;
```
```
        (*head) = (*head)->next;
```
```
    }
```
```
}
```
```
 
```

void release_2(struct node_occur **head)

```
{
```
```
    struct node_occur *temp = *head;
```
```
    *head = (*head)->next;
```
```
    while ((*head) != NULL)
```
```
    {
```
```
        free(temp);
```
```
        temp = *head;
```
```
        (*head) = (*head)->next;
```
```
    }
```
```
}
```

$ cc occurence.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: 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]: 1
Enter number: 2
Do you wish to continue [1/0]: 1
Enter number: 6
Do you wish to continue [1/0]: 1
Enter number: 1
Do you wish to continue [1/0]: 0
 
Displaying the occurence of each node in the list:
1	2	3	2	4	2	6	1	
***************************
  Number	Occurence
***************************
    1		2
    2		3
    3		1
    4		1
    6		1

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