C++ Program For Writing A Function To Get Nth Node In A Linked List

// C++ program to find n'th
// node in linked list
#include <assert.h>
#include <bits/stdc++.h>
using namespace std;

// Link list node
class Node {
public:
    int data;
    Node* next;
};

/* Given a reference (pointer to
pointer) to the head of a list
and an int, push a new node on
the front of the list. */
void push(Node** head_ref, int new_data)
{
    // Allocate node
    Node* new_node = new Node();

    // Put in the data
    new_node->data = new_data;

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

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

// Takes head pointer of
// the linked list and index
// as arguments and return
// data at index
int GetNth(Node* head, int index)
{
    Node* current = head;

    // The index of the
    // node we're currently
    // looking at
    int count = 0;
    while (current != NULL) {
        if (count == index)
            return (current->data);
        count++;
        current = current->next;
    }

    /* If we get to this line,
    the caller was asking
    for a non-existent element
    so we assert fail */
    assert(0);
}

// Driver Code
int main()
{
    // Start with the empty list
    Node* head = NULL;

    // Use push() to construct list
    // 1->12->1->4->1
    push(&head, 1);
    push(&head, 4);
    push(&head, 1);
    push(&head, 12);
    push(&head, 1);

    // Check the count function
    cout << "Element at index 3 is " << GetNth(head, 3);
    return 0;
}
// This code is contributed by rathbhupendra

// C++ program to find n'th node in
// linked list using recursion
#include <bits/stdc++.h>
using namespace std;

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

/*  Given a reference (pointer to pointer)
    to the head of a list and an int, push
    a new node on the front of the list. */
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 of the new node
    new_node->next = (*head_ref);

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

/* Takes head pointer of the linked list and
   index as arguments and return data at index.
   (Don't use another variable)*/
int GetNth(struct Node* head, int n)
{
    // If length of the list is less
    // than the given index, return -1
    if (head == NULL)
        return -1;

    // If n equal to 0 return node->data
    if (n == 0)
        return head->data;

    // Increase head to next pointer
    // n - 1: decrease the number of
    // recursions until n = 0
    return GetNth(head->next, n - 1);
}

// Driver code
int main()
{
    // Start with the empty list
    struct Node* head = NULL;

    // Use push() to construct list
    // 1->12->1->4->1
    push(&head, 1);
    push(&head, 4);
    push(&head, 1);
    push(&head, 12);
    push(&head, 1);

    // Check the count function
    printf("Element at index 3 is %d", GetNth(head, 3));
    getchar();
}