C Program to Check if Singly Linked List is Palindrome

This C Program checks whether the singly linked list is a palindrome. A palindrome is a pattern in list in which the contents when read from front is the same as when read from last.

Here is source code of the C Program to check whether a singly linked list is a palindrome. The C program is successfully compiled and run on a Linux system. The program output is also shown below.

```
/*
```

 * C Program to Check whether a Singly Linked List is a Palindrome

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

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

```
    count = create(&p);
```
```
    result = palin_check(p, count);
```
```
    if (result == 1)
```
```
    {
```

        printf("The linked list is a palindrome.\n");

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

        printf("The linked list is not a palindrome.\n");

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

int palin_check (struct node *p, int count)

```
{
```
```
    int i = 0, j;
```
```
    struct node *front, *rear;
```
```
 
```
```
    while (i != count / 2)
```
```
    {
```
```
        front = rear = p;
```
```
        for (j = 0; j < i; j++)
```
```
        {
```
```
            front = front->next;
```
```
        }
```

        for (j = 0; j < count - (i + 1); j++)

```
        {
```
```
            rear = rear->next;
```
```
        }
```
```
        if (front->num != rear->num)
```
```
        {
```
```
            return 0;
```
```
        }
```
```
        else
```
```
        {
```
```
            i++;
```
```
        }
```
```
    }
```
```
 
```
```
    return 1;
```
```
}
```
```
 
```
```
int create (struct node **head)
```
```
{
```
```
    int c, ch, count = 0;
```
```
    struct node *temp;
```
```
 
```
```
    do
```
```
    {
```
```
        printf("Enter number: ");
```
```
        scanf("%d", &c);
```
```
        count++;
```

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

```
        temp->num = c;
```
```
        temp->next = *head;
```
```
        *head = temp;
```

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

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

$ cc linklistpalin.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: 3
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]: 0
 
The linked list is a palindrome.

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