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Java Program For Comparing Two Strings Represented As Linked Lists

Last Updated : 23 Jul, 2025
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Given two strings, represented as linked lists (every character is a node in a linked list). Write a function compare() that works similar to strcmp(), i.e., it returns 0 if both strings are the same, 1 if the first linked list is lexicographically greater, and -1 if the second string is lexicographically greater.
Examples:

Input: list1 = g->e->e->k->s->a
       list2 = g->e->e->k->s->b
Output: -1

Input: list1 = g->e->e->k->s->a
       list2 = g->e->e->k->s
Output: 1

Input: list1 = g->e->e->k->s
       list2 = g->e->e->k->s
Output: 0
Java 
// Java program to compare two strings 
// represented as a linked list

// Linked List Class
class LinkedList 
{
    // Head of list
    Node head;  
    static Node a, b;

    // Node Class 
    static class Node 
    {
        char data;
        Node next;

        // Constructor to create 
        // a new node
        Node(char d) 
        {
            data = d;
            next = null;
        }
    }

    int compare(Node node1, 
                Node node2) 
    {
        if (node1 == null && 
            node2 == null) 
        {
            return 1;
        }
        while (node1 != null && 
               node2 != null && 
               node1.data == node2.data) 
        {
            node1 = node1.next;
            node2 = node2.next;
        }

        // if the list are different 
        // in size
        if (node1 != null && 
            node2 != null) 
        {
            return (node1.data > 
                    node2.data ? 1 : -1);
        }

        // if either of the list has 
        // reached end
        if (node1 != null && 
            node2 == null) 
        {
            return 1;
        }
        if (node1 == null && 
            node2 != null) 
        {
            return -1;
        }
        return 0;
    }
  
    // Driver code
    public static void main(String[] args) 
    {
        LinkedList list = new LinkedList();
        Node result = null;

        list.a = new Node('g');
        list.a.next = new Node('e');
        list.a.next.next = new Node('e');
        list.a.next.next.next = 
             new Node('k');
        list.a.next.next.next.next = 
             new Node('s');
        list.a.next.next.next.next.next = 
             new Node('b');

        list.b = new Node('g');
        list.b.next = new Node('e');
        list.b.next.next = new Node('e');
        list.b.next.next.next = 
             new Node('k');
        list.b.next.next.next.next = 
             new Node('s');
        list.b.next.next.next.next.next = 
             new Node('a');

        int value;
        value = list.compare(a, b);
        System.out.println(value);
    }
}
// This code is contributed by Mayank Jaiswal

Output: 

1

Time Complexity: O(M + N), where M and N represents the length of the given two linked lists.
Auxiliary Space: O(1), no extra space is required, so it is a constant.

Please refer complete article on Compare two strings represented as linked lists for more details!


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