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.

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/*
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 * C Program to Find Number of Occurences of All Elements in a Linked List

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

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void release(struct node **);
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void release_2(struct node_occur **);
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void display(struct node *);
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void disp_occur(struct node_occur *);
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int main()
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{
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    struct node *p = NULL;
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    struct node_occur *head = NULL;
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    int n;
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    printf("Enter data into the list\n");

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    create(&p);
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    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);
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    return 0;
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}
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void occur(struct node *head, struct node_occur **result)

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{
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    struct node *p;
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    struct node_occur *temp, *prev;
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    p = head;
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    while (p != NULL)
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    {
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        temp = *result;
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        while (temp != NULL && temp->num != p->num)

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        {
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            prev = temp;
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            temp = temp->next;
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        }
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        if (temp == NULL)
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        {
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            temp = (struct node_occur *)malloc(sizeof(struct node_occur));

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            temp->num = p->num;
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            temp->times = 1;
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            temp->next = NULL;
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            if (*result != NULL)
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            {
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                prev->next = temp;
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            }
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            else
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```
            {
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                *result = temp;
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            }
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        }
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        else
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```
        {
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            temp->times += 1;
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        }
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        p = p->next;
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    }
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}
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void create(struct node **head)
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{
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    int c, ch;
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    struct node *temp, *rear;
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    do
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```
    {
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        printf("Enter number: ");
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        scanf("%d", &c);
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        temp = (struct node *)malloc(sizeof(struct node));

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        temp->num = c;
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        temp->next = NULL;
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        if (*head == NULL)
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        {
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            *head = temp;
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        }
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        else
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```
        {
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            rear->next = temp;
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        }
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        rear = temp;
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        printf("Do you wish to continue [1/0]: ");

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

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    while (p != NULL)
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    {
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        printf("    %d\t\t%d\n", p->num, p->times);

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

void release_2(struct node_occur **head)

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