C Program to Find the First Common Element in Two Linked Lists

This C Program finds the first common element between the 2 given linked list.

Here is a source code of the C Program to find the first common element between the 2 given 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 the first Common Element between the 2 given Linked Lists

```
 */
```
```
#include <stdio.h>
```
```
#include <stdlib.h>
```
```
 
```
```
struct node
```
```
{
```
```
    int num;
```
```
    struct node *next;
```
```
};
```
```
 
```
```
void create(struct node **);
```
```
int find(struct node *, struct node *);
```
```
void release(struct node **);
```
```
void display(struct node *);
```
```
 
```
```
int main()
```
```
{
```
```
    struct node *p = NULL, *q = NULL;
```
```
    int result;
```
```
 
```

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

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    create(&p);
```

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

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    create(&q);
```
```
    printf("Displaying list1:\n");
```
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    display(p);
```
```
    printf("Displaying list2:\n");
```
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    display(q);
```
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    result = find(p, q);
```
```
    if (result)
```
```
    {
```

        printf("The first matched element is %d.\n", result);

```
    }
```
```
    else
```
```
    {
```

        printf("No matching element found.\n");

```
    }
```
```
    release (&p);
```
```
 
```
```
    return 0;
```
```
}
```
```
 
```

int find(struct node *p, struct node *q)

```
{
```
```
    struct node *temp;
```
```
 
```
```
    while (p != NULL)
```
```
    {
```
```
        temp = q;
```
```
        while (temp != NULL)
```
```
        {
```
```
            if (temp->num == p->num)
```
```
            {
```
```
                return p->num;
```
```
            }
```
```
            temp = temp->next;
```
```
        }
```
```
        p = p->next;
```
```
    }
```
```
 
```

    /*Assuming 0 is not used in the list*/

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

$ cc firstcommon.c 
$ ./a.out
Enter data into the list1
Enter number: 2
Do you wish to continue [1/0]: 1
Enter number: 8
Do you wish to continue [1/0]: 1
Enter number: 5
Do you wish to continue [1/0]: 1
Enter number: 6
Do you wish to continue [1/0]: 0
 
Enter data into the list2
Enter number: 3
Do you wish to continue [1/0]: 1
Enter number: 5
Do you wish to continue [1/0]: 1
Enter number: 9
Do you wish to continue [1/0]: 0
 
Displaying list1:
2	8	5	6	
Displaying list2:
3	5	9	
The first matched element is 5.

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