C Program to Find Nth Node from End of Linked List

This C Program prints the Nth node from the last node of a linked list. The approach used is to first point a pointer to a node which is N nodes ahead from the head. Then, move the Nth pointer and head pointer one node at a time till the Nth pointer has reached to the rear node. The pointer in the middle is the Nth pointer from the end.

Here is a source code of the C program to print the nth node from the last node of 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 Print Nth Node from the last of a Linked List

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

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

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

    printf("Enter the value n to find nth position from the last node: ");

```
    scanf("%d", &n);
```
```
    nthnode(p, n);
```
```
    release (&p);
```
```
 
```
```
    return 0;
```
```
}
```
```
 
```
```
void nthnode(struct node *head, int n)
```
```
{
```
```
    struct node *p, *q;
```
```
    int i;
```
```
 
```
```
    q = p = head;
```
```
 
```

    for (i = 0; i < n && q != NULL; i++)

```
    {
```
```
        q = q->next;
```
```
    }
```
```
    if (i < n)
```
```
    {
```

        printf("Entered n = %d is larger than the number of elements = %d in list. Please try again.\n", n, i);

```
    }
```
```
    else
```
```
    {
```
```
        while (q->next != NULL)
```
```
        {
```
```
            q = q->next;
```
```
            p = p->next;
```
```
        }
```

        printf("%d is %d nodes from the last node.\n", p->num, n);

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

$ cc nthnode.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: 4
Do you wish to continue [1/0]: 1
Enter number: 5
Do you wish to continue [1/0]: 0
 
Enter the value n to find nth position from the last node: 2
3 is 2 nodes from the last node.

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