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Friday, 07 July 2017 03:58

Write a function to get Nth node in a Linked List

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Write a GetNth() function that takes a linked list and an integer index and returns the data value stored in the node at that index position.


Input:  1->10->30->14,  index = 2
Output: 30  
The node at index 2 is 30


1. Initialize count = 0
2. Loop through the link list
     a. if count is equal to the passed index then return current
     b. Increment count
     c. change current to point to next of the current.


// C program to find n'th node in linked list
#include <stdio.h>
#include <stdlib.h>
#include <assert.h>
/* 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 off 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(struct Node* head, int index)
    struct Node* current = head;
    int count = 0; /* the index of the node we're currently
                  looking at */
    while (current != NULL)
       if (count == index)
       current = current->next;
    /* if we get to this line, the caller was asking
       for a non-existent element so we assert fail */
/* Drier program to test above function*/
int main()
    /* Start with the empty list */
    struct Node* head = NULL;
    /* Use push() to construct below 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)); 



Element at index 3 is 4
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