Squareroot(n)-th node in a Linked List

Given a Linked List, write a function that accepts the head node of the linked list as a parameter and returns the value of node present at (floor(sqrt(n)))th position in the Linked List, where n is the length of the linked list or the total number of nodes in the list.
Examples:

Input: 1->2->3->4->5->NULL
Output: 2

Input : 10->20->30->40->NULL
Output : 20

Input : 10->20->30->40->50->60->70->80->90->NULL
Output : 30

Simple method: The simple method is to first find the total number of nodes present in the linked list, then find the value of floor(squareroot(n)) where n is the total number of nodes. Then traverse from the first node in the list to this position and return the node at this position.
This method traverses the linked list 2 times.



Optimized approach: In this method, we can get the required node by traversing the linked list once only. Below is the step by step algorithm for this approach.

  1. Initialize two counters i and j both to 1 and a pointer sqrtn to NULL to traverse til the required position is reached.
  2. Start traversing the list using head node until the last node is reached.
  3. While traversing check if the value of j is equal to sqrt(i). If the value is equal increment both i and j and sqrtn to point sqrtn->next otherwise increment only i.
  4. Now, when we will reach the last node of list i will contain value of n, j will contain value of sqrt(i) and sqrtn will point to node at jth position.

C++

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// C++ program to find sqrt(n)'th node 
// of a linked list 
  
#include <bits/stdc++.h>
using namespace std;
  
// Linked list node 
class Node 
    public:
    int data; 
    Node* next; 
}; 
  
// Function to get the sqrt(n)th 
// node of a linked list 
int printsqrtn(Node* head) 
    Node* sqrtn = NULL; 
    int i = 1, j = 1; 
      
    // Traverse the list 
    while (head!=NULL) 
    
        // check if j = sqrt(i) 
        if (i == j*j) 
        
            // for first node 
            if (sqrtn == NULL) 
                sqrtn = head; 
            else
                sqrtn = sqrtn->next; 
              
            // increment j if j = sqrt(i) 
            j++; 
        
        i++; 
          
        head=head->next; 
    
      
    // return node's data 
    return sqrtn->data; 
  
void print(Node* head) 
    while (head != NULL) 
    
        cout << head->data << " "
        head = head->next; 
    
    cout<<endl; 
  
// function to add a new node at the 
// beginning 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 off the new node 
    new_node->next = (*head_ref); 
      
    // move the head to point to the new node 
    (*head_ref) = new_node; 
  
/* Driver program to test above function*/
int main() 
    /* Start with the empty list */
    Node* head = NULL; 
    push(&head, 40); 
    push(&head, 30); 
    push(&head, 20); 
    push(&head, 10); 
    cout << "Given linked list is:"
    print(head); 
    cout << "sqrt(n)th node is " << printsqrtn(head); 
      
    return 0; 
  
// This is code is contributed by rathbhupendra

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C

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// C program to find sqrt(n)'th node 
// of a linked list
  
#include<stdio.h>
#include<stdlib.h>
  
// Linked list node 
struct Node
{
    int data;
    struct Node* next;
};
  
// Function to get the sqrt(n)th 
// node of a linked list
int printsqrtn(struct Node* head)
{
    struct Node* sqrtn = NULL;
    int i = 1, j = 1;
      
    // Traverse the list
    while (head!=NULL)
    {   
        // check if j = sqrt(i)
        if (i == j*j)
        {   
            // for first node
            if (sqrtn == NULL)
                sqrtn = head;
            else
                sqrtn = sqrtn->next; 
              
            // increment j if j = sqrt(i)    
            j++;
        }
        i++;
          
        head=head->next;
    }
      
    // return node's data
    return sqrtn->data;
}
  
void print(struct Node* head)
{
    while (head != NULL)
    {
        printf("%d ", head->data);
        head = head->next;
    }
    printf("\n");
}
  
// function to add a new node at the 
// beginning 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;
}
  
/* Driver program to test above function*/
int main()
{
    /* Start with the empty list */
    struct Node* head = NULL;
    push(&head, 40);
    push(&head, 30);
    push(&head, 20);
    push(&head, 10);
    printf("Given linked list is:");
    print(head);
    printf("sqrt(n)th node is %d ",printsqrtn(head));
      
    return 0;
}

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Java

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// Java program to find sqrt(n)'th node 
// of a linked list 
  
class GfG 
{
  
// Linked list node 
static class Node 
    int data; 
    Node next; 
}
static Node head = null;
  
// Function to get the sqrt(n)th 
// node of a linked list 
static int printsqrtn(Node head) 
    Node sqrtn = null
    int i = 1, j = 1
      
    // Traverse the list 
    while (head != null
    
        // check if j = sqrt(i) 
        if (i == j * j) 
        
            // for first node 
            if (sqrtn == null
                sqrtn = head; 
            else
                sqrtn = sqrtn.next; 
              
            // increment j if j = sqrt(i) 
            j++; 
        
        i++; 
          
        head=head.next; 
    
      
    // return node's data 
    return sqrtn.data; 
  
static void print(Node head) 
    while (head != null
    
        System.out.print( head.data + " "); 
        head = head.next; 
    
    System.out.println(); 
  
// function to add a new node at the 
// beginning of the list 
static void push( int new_data) 
    // allocate node 
    Node new_node = new Node(); 
      
    // put in the data 
    new_node.data = new_data; 
      
    // link the old list off the new node 
    new_node.next = head; 
      
    // move the head to point to the new node 
    head = new_node; 
  
/* Driver code*/
public static void main(String[] args) 
    /* Start with the empty list */
    push( 40); 
    push( 30); 
    push( 20); 
    push( 10); 
    System.out.print("Given linked list is:"); 
    print(head); 
    System.out.print("sqrt(n)th node is " +
                        printsqrtn(head)); 
  
// This code is contributed by prerna saini

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Python3

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# Python3 program to find sqrt(n)'th node 
# of a linked list 
  
# Node class 
class Node: 
  
    # Function to initialise the node object 
    def __init__(self, data): 
        self.data = data 
        self.next = None
  
# Function to get the sqrt(n)th 
# node of a linked list 
def printsqrtn(head) :
  
    sqrtn = None
    i = 1
    j = 1
      
    # Traverse the list 
    while (head != None) :
      
        # check if j = sqrt(i) 
        if (i == j * j) :
          
            # for first node 
            if (sqrtn == None) :
                sqrtn = head 
            else:
                sqrtn = sqrtn.next
              
            # increment j if j = sqrt(i) 
            j = j + 1
          
        i = i + 1
          
        head = head.next
      
    # return node's data 
    return sqrtn.data 
  
def print_1(head) :
  
    while (head != None) :
        print( head.data, end = " "
        head = head.next
    print(" ")
  
# function to add a new node at the 
# beginning of the list 
def push(head_ref, new_data) :
  
    # allocate node 
    new_node = Node(0)
      
    # 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 
    return head_ref
  
# Driver Code 
if __name__=='__main__'
  
    # Start with the empty list 
    head = None
    head = push(head, 40
    head = push(head, 30
    head = push(head, 20
    head = push(head, 10
    print("Given linked list is:"
    print_1(head) 
    print("sqrt(n)th node is "
              printsqrtn(head))
      
# This code is contributed by Arnab Kundu

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C#

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// C# program to find sqrt(n)'th node 
// of a linked list 
using System;
public class GfG 
  
// Linked list node 
class Node 
    public int data; 
    public Node next; 
static Node head = null
  
// Function to get the sqrt(n)th 
// node of a linked list 
static int printsqrtn(Node head) 
    Node sqrtn = null
    int i = 1, j = 1; 
      
    // Traverse the list 
    while (head != null
    
        // check if j = sqrt(i) 
        if (i == j * j) 
        
            // for first node 
            if (sqrtn == null
                sqrtn = head; 
            else
                sqrtn = sqrtn.next; 
              
            // increment j if j = sqrt(i) 
            j++; 
        
        i++; 
          
        head=head.next; 
    
      
    // return node's data 
    return sqrtn.data; 
  
static void print(Node head) 
    while (head != null
    
        Console.Write( head.data + " "); 
        head = head.next; 
    
    Console.WriteLine(); 
  
// function to add a new node at the 
// beginning of the list 
static void push( int new_data) 
    // allocate node 
    Node new_node = new Node(); 
      
    // put in the data 
    new_node.data = new_data; 
      
    // link the old list off the new node 
    new_node.next = head; 
      
    // move the head to point to the new node 
    head = new_node; 
  
/* Driver code*/
public static void Main(String[] args) 
    /* Start with the empty list */
    push( 40); 
    push( 30); 
    push( 20); 
    push( 10); 
    Console.Write("Given linked list is:"); 
    print(head); 
    Console.Write("sqrt(n)th node is "
                        printsqrtn(head)); 
  
/* This code is contributed by 29AjayKumar */

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Output:

Given linked list is:10 20 30 40
sqrt(n)th node is 20

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