C Program To Check If A Linked List Of Strings Forms A Palindrome

Last Updated : 22 Jun, 2022

Given a linked list handling string data, check to see whether data is palindrome or not? Examples:

Input: a -> bc -> d -> dcb -> a -> NULL
Output: True
String "abcddcba" is palindrome.

Input: 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"); 
} 

/* 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 code 
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"): 
                        printf("false"); 
    return 0; 
}

Output:

true

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.

Please refer complete article on Check if a linked list of strings forms a palindrome for more details!