Python Program For Comparing Two Strings Represented As Linked Lists

Last Updated : 15 Jun, 2022
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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
Python 
# Python program to compare two strings 
# represented as linked lists

# A linked list node 
# structure
class Node:

    # Constructor to create 
    # a new node
    def __init__(self, key):
        self.c = key ; 
        self.next = None

def compare(list1, list2):
    
    # Traverse both lists. Stop when 
    # either end of linked list is 
    # reached or current characters 
    # don't match
    while(list1 and list2 and 
          list1.c == list2.c):
        list1 = list1.next 
        list2 = list2.next 

    # If both lists are not empty, 
    # compare mismatching characters 
    if(list1 and list2):
        return 1 if list1.c > list2.c else -1 

    # If either of the two lists has 
    # reached end
    if (list1 and not list2):
        return 1 

    if (list2 and not list1):
        return -1 
    return 0

# Driver code
list1 = Node('g')
list1.next = Node('e')
list1.next.next = Node('e')
list1.next.next.next = Node('k')
list1.next.next.next.next = Node('s')
list1.next.next.next.next.next = Node('b')

list2 = Node('g')
list2.next = Node('e')
list2.next.next = Node('e')
list2.next.next.next = Node('k')
list2.next.next.next.next = Node('s')
list2.next.next.next.next.next = Node('a')

print compare(list1, list2)
# This code is contributed by Nikhil Kumar Singh(nickzuck_007)

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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