nthnodefromend.cpp

// C program to find n'th node from end using slow and 
// fast pointers 
#include<stdio.h> 
#include<stdlib.h> 

/* Link list node */
struct Node 
{ 
int data; 
struct Node* next; 
}; 

/* Function to get the nth node from the last of a linked list*/
void printNthFromLast(struct Node *head, int n) 
{ 
struct Node *main_ptr = head; 
struct Node *ref_ptr = head; 

int count = 0; 
if(head != NULL) 
{ 
	while( count < n ) 
	{ 
		if(ref_ptr == NULL) 
		{ 
		printf("%d is greater than the no. of "
					"nodes in list", n); 
		return; 
		} 
		ref_ptr = ref_ptr->next; 
		count++; 
	} /* End of while*/

	while(ref_ptr != NULL) 
	{ 
		main_ptr = main_ptr->next; 
		ref_ptr = ref_ptr->next; 
	} 
	printf("Node no. %d from last is %d ", 
			n, main_ptr->data); 
} 
} 

void push(struct Node** head_ref, int new_data) 
{ 
/* allocate node */
struct Node* new_node = 
		(struct Node*) malloc(sizeof(struct Node)); 

/* put in the data */
new_node->data = new_data; 

/* link the old list off the new node */
new_node->next = (*head_ref);	 

/* move the head to point to the new node */
(*head_ref) = new_node; 
} 

/* Drier program to test above function*/
int main() 
{ 
/* Start with the empty list */
struct Node* head = NULL; 
push(&head, 20); 
push(&head, 4); 
push(&head, 15); 
push(&head, 35); 

printNthFromLast(head, 4); 
}