nth_node_from_end.cpp

// C program to find n'th Node in linked list
#include <stdio.h>
#include <stdlib.h>
#include<iostream>
using namespace std;
/* Link list Node */
struct Node{
    int data;
    struct Node* next;
};
void append(struct Node** head_ref, struct Node **tail_ref, int new_data)
{
    struct Node* new_node = new Node;
    new_node->data  = new_data;
    new_node->next = NULL;
    if (*head_ref == NULL)
       *head_ref = new_node;
    else
       (*tail_ref)->next = new_node;
    *tail_ref = new_node;
}
/* Function to get the nth node from the last of a linked list*/
int getNthFromLast(struct Node* head, int n);
/* Driver program to test above function*/
int main()
{
  int T,i,n,l,k;
    cin>>T;
    while(T--){
    struct Node *head = NULL,  *tail = NULL;
        cin>>n>>k;
        for(i=1;i<=n;i++)
        {
            cin>>l;
            append(&head, &tail, l);
        }
        printf("%d", getNthFromLast(head, k));
    }
    return 0;
}


/*Please note that it's Function problem i.e.
you need to write your solution in the form of Function(s) only.
Driver Code to call/invoke your function is mentioned above.*/

/* struct Node
 {
   int data;
   Node* next;
 }; */
/* Should return data of n'th node from the end of linked list */
int getLength(Node* head){
    Node* temp = head;
    int len=0;
    while(temp){
        temp = temp->next;
        len++;
    }
    return len;
}
int getNthFromLast(Node *head, int n){
    // Find total length of LL
    int len = getLength(head);
    // Nth from last means len-n+1 from start
    if(len<n)
        return -1;
    int index = len-n;
    Node* temp = head;
    while(temp && index){
        temp = temp->next;
        index--;
    }
    return temp->data;
       // Your code here
}