Check if a linked list of strings forms a palindrome
Last Updated :
26 Dec, 2022
Given a linked list handling string data, check to see whether data is palindrome or not?
For example,
Input : a -> bc -> d -> dcb -> a -> NULL
Output : True
String "abcddcba" is palindrome.
Output : a -> bc -> d -> ba -> NULL
Output : False
String "abcdba" is not palindrome.
The idea is very simple. Construct a string out of given linked list and check if the constructed string is palindrome or not.
C++
// Program to check if a given linked list of strings
// form a palindrome
#include <bits/stdc++.h>
using namespace std;
/* Link list node */
struct Node
{
string data;
Node* next;
};
// A utility function to check if str is palindrome
// or not
bool isPalindromeUtil(string str)
{
int length = str.length();
// Match characters from beginning and
// end.
for (int i=0; i<length/2; i++)
if (str[i] != str[length-i-1])
return false;
return true;
}
// Returns true if string formed by linked
// list is palindrome
bool isPalindrome(Node *node)
{
// Append all nodes to form a string
string str = "";
while (node != NULL)
{
str.append(node->data);
node = node->next;
}
// Check if the formed string is palindrome
return isPalindromeUtil(str);
}
// A utility function to print a given linked list
void printList(Node *node)
{
while (node != NULL)
{
cout << node->data << " -> ";
node = node->next;
}
printf("NULL\n");
}
/* Function to create a new node with given data */
Node *newNode(const char *str)
{
Node *new_node = new Node;
new_node->data = str;
new_node->next = NULL;
return new_node;
}
/* Driver program to test above function*/
int main()
{
Node *head = newNode("a");
head->next = newNode("bc");
head->next->next = newNode("d");
head->next->next->next = newNode("dcb");
head->next->next->next->next = newNode("a");
isPalindrome(head)? printf("true\n"):
printf("false\n");
return 0;
}
// Java Program to check if a given linked list of strings
// form a palindrome
import java.util.Scanner;
// Linked List node
class Node
{
String data;
Node next;
Node(String d)
{
data = d;
next = null;
}
}
class LinkedList_Palindrome
{
Node head;
// A utility function to check if str is palindrome
// or not
boolean isPalidromeUtil(String str)
{
int length = str.length();
// Match characters from beginning and
// end.
for (int i=0; i<length/2; i++)
if (str.charAt(i) != str.charAt(length-i-1))
return false;
return true;
}
// Returns true if string formed by linked
// list is palindrome
boolean isPalindrome()
{
Node node = head;
// Append all nodes to form a string
String str = "";
while (node != null)
{
str = str.concat(node.data);
node = node.next;
}
// Check if the formed string is palindrome
return isPalidromeUtil(str);
}
/* Driver program to test above function*/
public static void main(String[] args)
{
LinkedList_Palindrome list = new LinkedList_Palindrome();
list.head = new Node("a");
list.head.next = new Node("bc");
list.head.next.next = new Node("d");
list.head.next.next.next = new Node("dcb");
list.head.next.next.next.next = new Node("a");
System.out.println(list.isPalindrome());
}
}
// This code has been contributed by Amit Khandelwal
# Python program to check if given linked list of
# strings form a palindrome
# Node class
class Node:
# Constructor to initialize the node object
def __init__(self, data):
self.data = data
self.next = None
class LinkedList:
# Function to initialize head
def __init__(self):
self.head = None
# A utility function to check if str is palindrome
# or not
def isPalindromeUtil(self, string):
return (string == string[::-1])
# Returns true if string formed by linked list is
# palindrome
def isPalindrome(self):
node = self.head
# Append all nodes to form a string
temp = []
while (node is not None):
temp.append(node.data)
node = node.next
string = "".join(temp)
return self.isPalindromeUtil(string)
# Utility function to print the linked LinkedList
def printList(self):
temp = self.head
while (temp):
print(temp.data,end=" ")
temp = temp.next
# Driver program to test above function
llist = LinkedList()
llist.head = Node('a')
llist.head.next = Node('bc')
llist.head.next.next = Node("d")
llist.head.next.next.next = Node("dcb")
llist.head.next.next.next.next = Node("a")
print ("true" if llist.isPalindrome() else "false")
# This code is contributed by Nikhil Kumar Singh(nickzuck_007)
// C# Program to check if a given linked list
// of strings form a palindrome
using System;
// Linked List node
class Node
{
public String data;
public Node next;
public Node(String d)
{
data = d;
next = null;
}
}
public class LinkedList_Palindrome
{
Node head;
// A utility function to check if
// str is palindrome or not
bool isPalidromeUtil(String str)
{
int length = str.Length;
// Match characters from beginning and
// end.
for (int i = 0; i < length / 2; i++)
if (str[i] != str[length - i - 1])
return false;
return true;
}
// Returns true if string formed by linked
// list is palindrome
bool isPalindrome()
{
Node node = head;
// Append all nodes to form a string
String str = "";
while (node != null)
{
str = str+(node.data);
node = node.next;
}
// Check if the formed string is palindrome
return isPalidromeUtil(str);
}
/* Driver code*/
public static void Main(String[] args)
{
LinkedList_Palindrome list = new LinkedList_Palindrome();
list.head = new Node("a");
list.head.next = new Node("bc");
list.head.next.next = new Node("d");
list.head.next.next.next = new Node("dcb");
list.head.next.next.next.next = new Node("a");
Console.WriteLine(list.isPalindrome());
}
}
// This code has been contributed
// by PrinciRaj1992
<script>
// Javascript Program to check if a given linked list of strings
// form a palindrome
var head;
class Node{
constructor(val){
this.data = val;
this.next = null;
}
}
function isPalindromeUtil(str){
var length = str.length;
// Match characters from beginning and
// end.
for(var i = 0; i<length/2; i++){
if(str[i] != str[length-i-1])
return false;
}
return true;
}
// Returns true if string formed by linked
// list is palindrome
function isPalindrome(node){
// Append all nodes to form a string
var str = "";
while(node != null){
str += node.data;
node = node.next;
}
// Check if the formed string is palindrome
return isPalindromeUtil(str);
}
function printList(node)
{
while (node != null)
{
console.log(node.data + " ");
node = node.next;
}
}
head = new Node("a");
head.next = new Node("bc");
head.next.next = new Node("d");
head.next.next.next = new Node("dcb");
head.next.next.next.next = new Node("a");
isPalindrome(head) ? console.log("true") : console.log("false");
// This code is contributed by Yash Agarwal(yashagarwal2852002)
</script>
Time Complexity: O(n), where n is the number of nodes in the given linked list.
Auxiliary Space: O(m), where m is the length of the string formed by the linked list.
Check if a linked list of strings forms a palindrome